Moral emotions affect children’s pro-social behaviors. However, majority of studies on this topic focused on the negative moral emotions (e.g. anger, shame, and guilt etc.), the influence of positive moral emotions (such as love, reverence, and pride etc.) on pro-social behavior was largely unknown. Using two types of priming paradigms, the present study aims to test the effect of the positive moral emotions on preschool children’s comforting behavior, which was largely understudied compared to other prosocial behaviors (such as sharing). Study 1 tested 125 preschoolers (3-5 years) from one kindergarten in Chongqing, China. They were randomly assigned to experimental (n=62) and control groups (n=63). The experimental group was treated with imaginative priming in order to activate their positive moral emotions, i.e. children were asked to imagine that they lent their crayons to a partner who was drawing with them, whereas the children in control group were taught how to make a cute caterpillar. To improve the external validity of our study, we developed actual priming paradigm for Study 2. An actual event (rather than imagination) which was happened in real life was used to prime children’s positive moral emotions, i.e. children were asked to help clean up the desk. Additional 132 preschoolers were recruited from another kindergarten. Sixty-nine were assigned to the experimental group and 63 were assigned to the control group. After priming, Both groups were tested on a comforting task, where the children should comfort an injured experimenter (Study 1) or a sad experimenter (Study 2). Video recording during the experiments were replayed to the raters for coding purposes. All the raters had been trained, but they were blind to the purpose of the study. The results showed that: (1) In both studies, experimental groups performed significantly more comforting behavior compared with control groups [Study 1: F (1,119) = 4.51, p < .05, ηp2 = .036; Study 2: F (1,126) = 7.21, p < .01, ηp2 = .05], suggesting that positive moral emotions could increase children’s comforting behaviors. (2) Significant age differences in children’s comforting behavior were also showed in both studies [Study 1: F (2,119) = 9.07, p < .001, ηp2 = .13; Study 2: F (2,126) = 10.00, p < .001, ηp2 = .15]. Post hoc comparisons revealed more comforting behavior in both 4- and 5-year-old in contrast to 3-year-old, while no significant difference was observed between 4- and 5-year-old. (3) There is no evidence of interaction between moral emotions and age [Study 1: F (2,119) = .21，p = .82; Study 2: F (2,126) = .49，p = .62]. Our studies found that positive moral emotions could increase the comforting behavior in children from 3 to 5 years old. In addition, children’s comforting behavior increases with age, which co-occurred with development of cognitive and emotional abilities. The effects of positive moral emotions on comforting behavior showed no difference at the ages of 3, 4 and 5 years. Our findings may provide scientific evidences for fostering positive moral emotions in early cultivation of children’s comforting behavior during preschooler education.