Bi er (pinyin: bì ěr), also known as the mountain reed flute, is a single-reed gas-sounding instrument of the Kemu people. It is popular in the areas where the Kemu people live in Mengla and Jinghong, Xishuangbanna Dai Autonomous Prefecture, Yunnan Province.

The Qier tube body is made of reed, and the Kemu people often use the local mountain reed to make it. There are reed joints on the upper end of the tube, and the lower end is transparent. The side of the tube wall near the section is thinned, and a rectangular reed is carved with a sharp knife, the reed root is connected to the reed section, and the reed tongue faces down. There are three to five circular sound holes on the front of the tube body, but no back holes.

Qier has a full-bodied pronunciation, rich timbre, and loud volume, which can be used for solo performance. Suitable for outdoor playing, it is a commonly used musical instrument for young men and women in Kemu when they are in love, and they are often played for self-entertainment. The music includes "Playing Girl Tune", etc.