This experiment was to study the relationship between shoot and root system in perennial ryegrass at different stages of growth. The results are summarized as follows; 1. The dry weight of shoot was significantly correlated with the dry weight of root at both stages of growth. 2. The yield components of shoot and root systems were changed by the stages of growth. Thus, the dry weights of shoot and root were positive correlated with the number of tillers and roots at 60 days after sowing. But, the dry weights of shoot and root were positive correlated with the dry weight of root, the dry weight of tiller, length of plant and length of root at 90 days after sowing. 3. Maprirna variety was obtained a higher dry weights of shoot and root at 60 days after sowing, but, Alta variety was obtained at 90 days after sowing, respectively. 4. The dry weight of shoot was positive correlated with leaf area at both stages of growth. 5. The dry weight of shoot was significantly negative correlated with specific leaf weight at 60 days after sowing, but positive correlated with specific leaf weight at 90 days afikr sowing. 6. The dry weight of root was smcantly positive correlated with leaf area at 60 days after sowing, but not recognized at 90 days after sowing.