Abstract: In order to determine the optimum back-roof elevation angle of solar greenhouse for central Shaanxi plain,it was numbered the solar greenhouse which back-roof elevation angle was 35°,40°,45°,50° to be 1#,2#,3#,4#.We observed the air temperature,5 cm and 20 cm soil temperature,the inner surface temperature of back-roof and the frostbite performance of crop in the coldest month.The results showed that the order of thermal insulation property was 3#>2#>1#>4#,it's mean minimum air temperature in the 3# in Jan.was 9.3℃,mean air temperature was 11.3℃,the average of air temperature daily range was 11.4℃,the soil temperature and back-roof inner surface temperature of 3# was higher than that of other greenhouse.The result of analysis of variance indicated that there were a significant difference of the average of air temperature daily range between 3# and 1#,as well as between 3# and 4#.Mean minimum air temperature was lower than others',and it had a high significantly correlated with outside air temperature(r=0.708>r0.01).It was suggested that 45° was the optimum back-roof elevation angle in all back-roof elevation angles in central Shaanxi plain.

Key words: Solar greenhouse, Solar greenhouse, Back-roof, Elevation angle, Temperature