Coordination of the aerial servey, the author carried ground census on the population size of Red-crowned crane (Grus japonensis) in Khanka Lakes District from 1984 to 1986. According to the census in spring of 1984, the total number of Red-crowned crane is 72 individuals and 20 nests. So that this ground census has recorded 59 individuals more than the aerial survey of 13 individuals, and the percentage of nesting individuals in this flock is 55.6%, which is obviously higher than 36.9% of the average ratio in China. After this, in fall of 1984 and in spring of 1985 and 1986, we repeated the same censuses three times in the same districts, the results indicated that the flock of the crane in Khanka Lakes District is stable basically, but some individuals interchange with opposite flock of USSR because of gegraphical adjoin.So, we believe this flock in China and that flock in USSR belong to the same population and suggest two countries should act in concert to studing on this population in future. Meanwhile, the aerial servey cooperate with ground census, it is the best way for reducing missing crane and achieving to high precision of census. From this, total number of Red-crowned crane in China is 542 individuals (483+59 ind ividuals).