Abstract: The asymmetry of tension and compression of Mg-11Y-5Gd-2Zn-0.5Zr (WGZ115) magnesium alloy and its reason were studied through optical microscopy and scanning electron microscopy observation as well as tension and compression test at different temperatures.The results show that brittle rupture of the alloy occured during tensile test under 200℃.The tensile yield strength was higher than the compressive yield strength as the temperature was between 200℃ and 300℃,and the former was equal to the latter as the temperature was 300℃.While the former was lower than the latter as the temperature was higher than 300℃.Under the same temperature the compressive yield strength was higher than the tensile yield strength,and the maximum compressive strain was larger than the maximum tensile strain.The cracks were main transgranular extension during tension,and the secondary cracks led to brittle fracture rapidly at 25℃ to 200℃.Twin bands formed in the alloy during compression,and the alloy had good compression workability.