Between 2002 to 2003，we made a test of cow’s physiological and performance in part of Chongqing. We also examine the cow’s blood. The result showed that：(1) From June to September，the cow’s temperature of rectum and rate of respiration are higher than that in March to May or October to February (P<0.05)；(2) The daily lactation between March to May and October to February are （23.5±4.2）kg/d（n=31）、（22.1±5.3）kg/d（n=43），also higher than (17.6±5.1) kg/d（n=52）（P<0.05）which in June to September. (3)In heat stress, the density of K+、Cl-、iCa 2+ in serum of cows are higher than other times. (P<0.05) .But the proteins in serum of cows are lower, the activity of alkaline phosphatase drop 38.96 percent and the activity of α-anylase drop 8.52 percent, the activity of GTP raise 3.74 percent.(4) In heat stress, the fecundation insemination of cow slower than the other times, but the diseases in heat stress are more .