Four Chinese Yellow cattle steers were selected to study the effect of the level of feed intake on the urinary excretion of purine derivatives (PD). The rations of the experiment were mixed rations consisting of a roughage and concentrate in the ratio of 60:40. Four steers were fed at four fixed levels, 95, 80, 60 and 40% of “voluntary intake”, using a 4 × 4 Latin square design. The apparent digestibility of organic matter was not significant different among intake levels. The daily excretion of PD showed a linear response to the level of intake. PD excretion (Y, mmol/d) was correlated to digestible organic matter intake (X, kg/d) according to the following equation, Y=20.64X +12.47 (R²=0.94, n=4; P<0.01). The results indicated that PD excretion in the urine can be used as an index for estimating microbial protein supply in Chinese Yellow cattle.