This study was carried out to determine the effect of plant competition between red clover and Kentucky bluegrass with different rates ,of botanical composition on the yield and nitrogen content of the plants, and nitrogen accumulation of the pasture soil. The botanical composition rates were as follows: Red clover: Kentucky bluegrass=1 : 1, 1 : 3, 1 : 5 and 1 : 7, reversely Kentucky bluegrass: Red clover=1 : 1, 1 : 3, 1 : 5 and 1 : 7, respectively. The results obtained in this study were as follows: 1. The botanical composition which magnitude of the increased yield was dependent upon the rate 1 : 3 in red clover-Kentucky blue grass mixture. 2. The plant nitrogen contents increased in clover-grass mixture more than in the pure Kentucky bluegrass stand. 3. Accumulation of soil nitrogen was affected by red clover and increased with high clover density than low. 4. Yield per plant in the mixture, clover Kentucky=1 : 3, was the highest.