The character and measure method of L-cysteine were summarized briefly,the simple and fast optical rotation method and absorbency method were discussed.The experimental data was analog computed by Statistic soft,the optical rotation model for determination of L-cysteine is y=0.146657x~2+0.05249,the variance R=0.99979,and the absorbency model for determination of L-cysteine is y=10842.1x,the variance R=0.99898. The optical rotation method and absorbency method for determination of L-cysteine were compared,ac...