The variations of muscle tissus , peroxidase and Ca2 2ATPase activities and Vp (pasteurization value) were investigated with the fresh samples of grass carp ( Ctenopharyngodon idellus ) heated at different temperatures , thus revealing the mechanism of denaturation of muscle protein by heating. The experimental results showed the great difference in muscle tissue structure before and after the samples heated. In the initial stage of heating the water loss accounted for 50 % of the total. When the samples were separately heated at 75 , 85 , and 95 ℃, fh values (dehydration curve slope) were 5 , 4. 1 and 1. 7 , respectively , while Vp reaching 40 minutes were 22 , 8 and 5 min , respectively. As to the time for deactivation of peroxidase in the heated samples at the various temperatures , it varied from 38 , 10 and to less than 6 min , respectively and the deactivation rates of Ca2 2ATPase in 1 min were 50 % , 88 % and 100 % , respectively. Consequently , the higher temperature the sample was heated , the faster rate of thermocon ductivity , the lower rate of water loss , and the faster rate of peroxidase deactivation it was. Also , the Vp for the least requirement of pasteurization ( Vp ≥40min) was obtained.