‘Liaobai No.21’ is a mid-late maturing Chinese cabbage variety．Its growing period is about 81 days．Its parents ‘S7-1’ comes from ‘Qingbanghetou’ and ‘S7-2’ comes from ‘Tianjinqingmaye’.They developed by crossing through many generations to inbred self-incompatible lines.This hybrid had vigorous growth and high uniformity of plants group.The outside leaves were dark green and the petiole was light green.Its leaf head was long cylinder-shaped.The ‘Liaobai No.21’was 49.6 cm in height and 59.0 cm in stretch.Its leaf head was 41.2 cm in height and 14.6 cm in diameter.The single plant weight was about 3.5 kg and the net product ratio of 84.6%.The artificial inoculation resistant to downy mildew and soft rot,high resistance to TMV.Its output was about 8 540.00 kg/667m2．It was suitable to be cultivated in Liaoning,Shandong,Hebei,and Jilin,etc.