Abstract: In order to analyze the effects of 10℃ and 15℃ low temperature treatment on watermelon seedlings,some physiological characters such as the light reaction activity,soluble sugars,proline(content)and the activities of POD(peroxidase)and APX(ascorbate peroxidase)were investigated in(watermelon)seedlings at the age of four leaves after low temperature stress.The results indicated that,the relative light reaction activities of varieties No.4 and No.6 are lower that of varieties No.2 and No.5,the content of soluble sugar and proline in the former two varieties increased rapidly at early time point of 15℃ stress,but that of the later two varieties increased steadily long after treated under 10℃ low(temperature).Compared with the respective control,the activities of POD and APX displayed a trend to increasing at 15℃ stress declining at 10℃ stress,and APX changed less than POD to some degree centigrade.(Considering)all the comprehensive physiological indices in this experiment,varieties No.2 and No.5 are relatively chilling-tolerant and varieties No.4 and No.6 are chilling-sensitive ones.Meanwhile,the light reaction activity,the contents of soluble sugar and proline could be applied to evaluated watermelon(chilling)tolerance as the main physiological performance.