How do I fix leaking pipe in my basement?

http://www.houserepairguides.com/find-repair-leaky-plumbing-drain-lines/

Is this a drain pipe of supply pipe? Is it cracked or a seam? A photo would help. You may need a plumber.

Linda,

Is it leaking from a connection with another pipe, from a valve, or from a hole in the pipe? By "main line" do you mean your supply line that comes into your house? If so, you need to temporarily shut the water off using the valve handle near where your water comes into your house. Then, open your sink faucet to relieve any pressure in the line. You do not want to risk a pipe bursting. As to how to fix it it's hard to say without more info or a picture. With the water off, you can evaluate what you need to fix the leak. If you give us more info, we can give you better advice.

I agree that a few pictures would help. Are you even sure it's a water pipe and not a sewer line? A flex seal tape or caulk is a temporary fix until you can get a professional out to check it.