Abstract: The test dealt with main research on the southern greenhouse sun shading and cooling result under different periods in one day and the influence on growing and output of sweet pepper. The result indicates that the result of lowering temperature is remarkable under different treatments, sunshading can reduce by 7 degrees Centigrade at most. But there is no very big difference of cooling effects under different periods and time lengths, and it is the same basically to lower the temperature effectively and the temperature lowering time. Sunshade and cooling impact on sweet pepper growth and output differs greatly under different periods, sun shading to cool from 12:00 at noon to 15:00 in the afternoon, net photosynthetic rate is the highest, the content of blade chlorophyll increases, promotes reproduction to grow, raise a fruit rate, previous output of the sweet pepper and total output are raised remarkably. Moving forward and lengthening the period of time of sunshading and cooling, the plant displays the excessive growth, the content of chlorophyll, net photosynthetic rate and the number of fruit per plant decrease, and the output is obviously reduced.