Objective To explore the relationship between social support and prosocial tendencies among the left-home kids in primary school, and provide theoretical reference to healthy growth education and positive qualities development of the left-home kids. Methods A total of 156 left-home kids and 163 non left-home kids were surveyed with Social Support Scale and Prosocial Tendencies Measure;Descriptive statistics, the T test, correlation and regression analysis were adopted to process the data. Results Social support and prosocial tendencies status of left-home kids was in medium high level;There were no significant differences on scores of subjective support, support utilization and 6 types of prosoical tendency between the left-home kids and non left-home kids;Left-home kids' objective support scores were significantly lower than that of non left-home kids (P<0.05).As for left-home kids, there was a certain degree of positive correlation between social support and prosocial tendencies(r=0.04~0.25, P<0.05 or <0.01).Subjective support was the significantly positive predictor for the public, anonymous, altruistic, compliant, dire prosocial tendencies.Support utilization was the significantly positive predictor for emotional prosocial tendency. Conclusions The more social support leads to the more prosocial tendencies among the left-home kids in primary school.Subjective support and support utilization are the main factors of prosocial tendencies.