Practice has proved that when the temperature changed between-2 and 5 ℃,its effect on weight gain of fattening cattle was extremely significant,whereas the temperature changed between 5 to 12 ℃,its effect was less.When barn’s NH3 content in the air changed between 20-30 mg/m3,it affected the weight gain of fattening cattle significantly.Environmental humidity and animal density had no significant effect on weight gain of fattening cattle when they were changed between 1 and 2 level,but the effect was rather great when they changed between 2 and 3 level.