How to do I get to Terminal of Beijing Capital Airport 1 via subway(wudaokou station)?

If you want to take the subway, from Wudaokou, you can take the subway line 13 to reach Xizhimen Station where you can change to line 2 to reach Dongzhimen Station. From there, you can take the airport express line to reach the airport directly.
In my opinion, it is suggested to take a taxi to reach Beihang University (North Gate), where you can find the direct airport shuttle bus line 5 to reach the airport directly.