I'll be going to Beijing. My flight ETA:11.45pm. How do i go to 29 Xueyuan Road, Haidian District?

At that time, you can take the Airport Night Bus Yonghegong Line to Sidaokou East and transfer to Night Bus Line 3 to Erligou Dongkou. After that, walk east and then north about 250m to take Night Bus Line 14 to Chengfu Lukou South. Get off the bus and then you can see your destination.