Please how much does it cost to take a taxi from Beijing capital airport to Mutianyiu great wall?

Petra, it is really a long way from the airport. It is suggested you charter a car at the airport for one day. You can find the branch of eHi car services at 1F of T2 and T3. The cost for a car varies from CNY120 to CNY600 depending on different car types.
One way trip to the Great Wall from the airport may cost CNY200 by cab.