Abstract:Recent researches on basic chromosome numbers of 601 taxa including 72 genera of the subfamily Chloridoideae are reviewed. Two main basic chromosome numbers occur in the majority of chloridoid genera, i.e. 9 and 10. Evidence indicates that x=9 and 10 are palepolyploid and aneuploid deviation basic chromosome numbers. Cytological characters have significant systematic value in recognizing supra-generic group in the Chloridoideae. An evolutionary trend of basic chromosome numbers is proposed： x=6→x=5→x=10→x=9. The primitive diploid group with 2n=2x=lO might have been extinct in the early, evolution.