Abstract: The bionomics and contr01 measures of Lecanium kuwanai Kanda., seriously damaged Japan pagodutree，Siberia elm and other tree in northwest China，are reported in this paper．It Occurs one generation a year，overwinters usually as 2 year old nymph under barks and sucks exudate from barks or leaves．7 species of natural enemies were found．Control measures such as using 1：0．5：1500(Dimethoate：DDVP：water) at the time of nymph emerging，replanting mixed forests instead of pure forests and protecting and appling natural enemies are proposed．