Employing the pot experiment of the complete random block design with 6 replications,four varieties ofrnjaponica rice (Fujisaka 5,Honenwase,Akitakomachi and Taichung 65) were used to study the varietal differ-rnences in leaf nitrogen content (LNC) and leaf area during mature period,their relation and effects to the ripenrning rate. The results showed that(1) thee were varietal differences in LNC at the heading stage and the LNCrndecrease rate during the matue period,the high LNC at the heading stage was related to the rapid LNC de-rncrease. (2) There were two phases of the leaf area changing process during the mature period,first was thernstable,and second was the decreased phase. There was varietal difference in the critical time of phase 1 andrnphase 2. The hign leaf area in the phase 1 was in relation to the rapid leaf area decrease in the phase 2. It wasrnnot found that there was relation between the leaf quality and quantity. (3)It wa unfavorable to the ripeningrnrate for the high leaf area at the heading stage and the rapid decrease of the leaf area during the mature peri-rnod. (4)It was put forward that the super high yield rice variety should possess the not very high leaf area andrnhigh LNC at the heading stage,slow senescence in the leaf area during the mature period.