Abstract: Three mutants with high drought tolerance (SP-64, SP-119, SP-17) have been screened from plants regenerated from the embryogenic calli of the Lolium perenne variety Derby, which were carried aboard by the Shenzhou No.7 spaceship. This paper presents the results of an evaluation of the physiological responses to drought treatment for these 3 mutants. As drought duration increased, the relative water content and chlorophyll content of the mutants decreased, whereas malondialdehyde (MDA) and soluble proline content increased. However, the 3 mutants’ superoxide dismutase (SOD) activities at first decreased and then increased. The variation ranges of indices were different for each mutation. A comprehensive analysis of these indices suggests that drought tolerance decreased in the order of SP-64, SP-119 and SP-17, which is consistent with the results of the apparent permanent wilting index (APWI). These results indicate that space mutation could induce the mutagenesis of drought resistance and so provide new germplasm resources for the breeding of turfgrass varieties.