You can go to Ostia Antica by the subway ticket of Rome.
You must change to the Ostia Lido line by EUR Magliana of a subway B line.
If you are lucky,you can go with a ticket once.
but it is better to purchase a 1day-ticket, since time spends to connection depending on a time zone or days.
After investigating the time of a subway in the following address,Let's go out.
Moreover, since Ostia Antica is near from an airport,
after you inspect this previously, You also have a method of going to Rome.
To reach this interesting site take the metro to Pyramido and then the train from Piazza S Paolo , next door. Ticket costs 1 Euro to and fro. On arrival at Ostia Antica exit the station and cross the footbridge. Continue straight ahead until you reach the site. It is only a few minute's walk.
There are swift new trains that take you from the Metro station at San Paolo (Piramide) directly to Ostia Antica - if you are going to the beach at Ostia, there are train stops for Lido North and Lido Central, - also all the way to the end, at Cristoforo Colombo, you will then take the local bus "MARE" that stops all along the public beach - gates 1 through 8.
From downtown Rome, it’s a 45-minute trip to Ostia Antica, with a combination of a Metro ride and local commuter train ride. As of May 2007 the cost for one Metro round-trip ticket is 2 euros.
If you get a Rome Pass (http://www.romapass.it/english), which includes a 3-day transportation ticket valid on the Metro, the tram, buses, and commuter rail lines, you can avoid the extra time needed to buy separate tickets. With the Rome Pass you can also get free or discounted admission to this wonderful archeological sight.
From Rome, take the Metro’s Red Line (Line B) to the Piramide stop (it is across the street from the Pyramid of Cestius). Exit and walk up the stairs staying to the right, following signs for the “Ingreso (entrance) Roma-Lido” train, which you will ride to Ostia Antica. When you get off the train at Ostia Antica’s station, cross the road by way of the blue footbridge and walk directly down Via della Stazione di Ostia Antica, continue to the parking lot. The entrance is on the left.
A great way to go from Rome to Ostia and at a very reasonable rate. You will think you are at the wrong place when you arrive at the trash dump where you take the boat to Ostia so brace yourself and your cab driver should know that you're in the right place. You will see a sign in the shabby parking lot indicating the direction for the Ostia Antica boat - IGNORE that sign and walk down the little concrete walkway to the right that advertises the boats - Battelli di Roma, and there you will find boat. After two hours the boat docks at Ostia Antica. Maps are available or you can hire a guide.
Be sure to check with the people at Battelli to make sure the boat is actually making the trip on the day you want to go - days are not reliable and they cancel for any number of reasons!
Website below gives you phone numbers and contact information.
Ostia Antica is only 20 km from Rome. How to get there?. Is easy take metro line B to Piramide metro station and from there take the train lido to Ostia Antica. When you arrive there just follow the sings to get the ruins. It takes about 30 minutes and you dont need to buy ticket if you have metro card for 3 days o 1 week or just buy single ticket.
Ostia Antica esta a unos 20 km de Roma. Es muy facil llegar, coge el la linea B del metro y bajate en Piramide y desde alli coge el tren lido que esta en el anden de enfrente y bajate en la estacion de tren de ostia antica. Tarda unos 30 minutos y no es necesario comprar billete de tren porque es valido el mismo billete de metro.
From Rome's Ostiense (stazione S Paolo) take the train leaving from binario 1 for the Lido. A normal biglietto for one euro will suffice.
Jump out of the train at Ostia Antica, just cross the busy street using the pedestrian bridge. It's just a five minutes walk away.