Moral outrage is an important moral emotion. It refers to the anger or disgust that an individual generates as a third party whose interests are not affected when he witnesses the violation of moral rules. The core of morality is fairness. Most of previous domestic research on children’s distribution fairness focuses on the number distribution, but there is little research on the value distribution. Therefore, it is necessary to exam whether children’s moral outrage has differences between unfair number distribution and unfair value distribution. In addition, would children’s moral outrage lead to third party justice? Third party justice refers to the third party’s judgments based on their understanding of the organization's unfair events, resulting in moral emotions such as anger and hostility, and making various interventions. Third party punishment and third party compensation are two typical third party justice behaviors. Then, if children need to pay the price, will they still maintain third party justice? But until now, there is little research exploring the influence of children’s moral outrage on their third party justice from the perspective of cost. Therefore, the aim of the present study is to explore the developmental characteristics of children’s moral outrage in senior kindergarten, grade 2 and grade 4 of primary school, and the influence of children’s moral outrage on third party justice under different cost conditions. This study further enriches the theoretical system of children’s moral outrage, and provides a reference for schools to guide children to form correct concepts of social justice and behave fairly in moral education. Our hypotheses were as follows: (1) Children’s moral outrage increased with the growth of grade. The unfair number distribution led to more moral outrage than the unfair value distribution. And there was a significant interaction between grade and unfair distribution type in children’s moral outrage. (2) Children’s moral outrage impacted their third party justice, and children induced by moral outrage were more inclined to show their third party justice under the condition of no cost than under the condition of cost. In experiment 1, 106 children in senior kindergarten, grade 2 and grade 4 of primary school were investigated the differences of their moral outrage in grade and unfair distribution type. The results showed that: (1) Children’s moral outrage showed a trend of increasing with the growth of grade. (2) The scores of children’s moral outrage caused by unfair number distribution were significantly higher than those caused by unfair value distribution. (3) The scores of children’s moral outrage caused by unfair number distribution were significantly higher than those caused by unfair value distribution in senior kindergarten and grade 2, while there was no significant difference in the scores of 4th grade children’s moral outrage between unfair number distribution and unfair value distribution. In experiment 2, 57 primary school children were explored the influence of their moral outrage on third party justice under different cost conditions. The results were as follows: (1) The children induced by moral outrage were more inclined to show third party justice, and more willing to compensate the victims. (2)Under different conditions of inducing moral outrage, whether it need to pay a price or not would not impact children’s third party justice. In conclusion, the present study demonstrates that children’s moral outrage develops with the growth of grade and affects their third party justice.