This may help you. As user Ithos explained to another person in this Forum with that question:
"Log into Google Calendar using Safari. To the right of the calendar name you want to share, click on the little triangle and choose "Calendar settings". If it is a public calendar, get the public ICAL address of the calendar. Copy it to the clipboard. Otherwise, if it's only for your use, copy the private ICAL address to the clipboard.
Open iCal (in Lion). Click Calendar->Subscribe... Paste the address you copied in the previous step into the "Calendar URL" field. Click Subscribe. In the sheet that appears, choose "iCloud" in the "Location" pop-up menu. Set other settings as you see fit. Then click "OK". iCal should report (in the title bar) that it is updating.
Now go to any of your iOS 5 devices that are associated with the same iCloud account (Apple ID). Open the Calendar app. Click the "Calendar" button in the upper left to view your list of calendars. The calendar you subscribed to on your Mac will appear as a subscribed calendar in your list of "iCloud" calendars.
Hope this helps.
By the way... If you want to subscribe to a Google calendar on only one iOS device, take the link you copied in the above step, paste it into an e-mail, and send it to yourself. (There are other ways to get the link to your iOS device, but this is probably the easiest.) On the iOS device, open the mail, click on the link, and Calendar will ask if you want to subscribe to the shared calendar. This type of sharing has been there for a long time, and still exists. But if you want to have a calendar subscription on all of your (multiple) iOS devices, you have to repeat the subscription step on every device. Locating the subscription on iCloud (as described above) eliminates this issue."