Hello. I'm going to stay at Sanlitun, Beijing. May i know if there is any halal restaurant nearby?

Yes, in Sanlitun area, there are several halal restaurants. Here list for your reference.

Miyang Zhuti Canba, located at No. 4 Zhongguohong Street, East Gongti Road.
Xinjiang Red Rose Halal Restaurant, located at No. Wugongqu Sidui, Lane 7, Xingfu Yicun.
Mahua Restaurant, located at No. 2 Baijiazhuang Xili.
Khan Baba, located at Sanlitun Soho.