Effects of colchicine treatment date,concentration,treatment time and cultivar tolerance to colchicine on production of autotetraploid rice was investigated.The results indicated that the percentage of plant chromosome doubling was different,when the date of colchicine treating buds was different.The buds were treated with colchicine before April 15,the percentage of plant chromosome doubling was the highest.The per- centage of plant chromosome doubling were affected by colchieine concentration and treat- ment time.The optimum combination was that the buds were treated for 48 h with 0.1 ~//00 colchicine,or for 24 h with 0.2% colchicine.Tolerance to colchicine was different be tween cultivars.Zhongzuo 9025 has the strongest tolerance to colchicine,the recovery per- centage of buds is 92.4%,and the percentage of plant chromosome doubling is 38.7%. Yanzhou 14 is most susceptible to colchicine,and recovery percentage of buds is only 10.6%.