from Beijing to Xizhazi Village by taxi

Alex, it's too expensive to take a taxi. According to what I found, it costs at least CNY 200 from Huairou to Xizhazi. You need to pay CNY154 at least if you want to catch a taxi from Beijing to Huairou. But I am afraid that the driver won't pick you up because he may not get a passenger from Huairou to Beijing at night. So I guess you should pay around CNY 500 if you plan to take a taxi from Beijing to Xizhazi at night.

Here is another option. You may take No.916 bus from Dongzhimen to Huairou Bus Station. It costs CNY 12 to 15. It's cheap but the bus is very crowded. The last bus departs at 19:00. Then you can catch a taxi from the bus station to Xizhazi.