I will be in Beijing from 21 Jan 2017 - 26 Jan 2017.

Well, it is suggested you go to Yuyuantan Park or Taoranting Park. There, you can attend the Ice & Snow Festival.
Admiring beautiful flowers in the Grand View Park, Fragrant Hill Park, and BJ Botanical Garden is also recommended.
If you have enough time, going to Longqing Gorge is another good choice. There is the Ice Lantern Carnival and you are suggested to stay there until the night to see the dazzling scenery there.