Prospective memory (PM) refers to the ability to remember and complete planned tasks in the future, which relies on working memory (WM) for encoding and maintaining the intention. Implementation intention is a useful strategy for improving PM function in adults. Yet the effect of implementation intentions in children, and whether factors such as age, gender, and WM capacity could modulate its effect remains unclear. In this study, we examined the effect of implementation intentions on PM in 154 children at 7-11 years of age. The standard group received standard instructions on PM task, whereas the implementation intention group received additional PM instruction, which comprised the "if . . . then . . ." format and guided visual imagery of the PM scenario. Participants completed the computer-based PM tasks (tapping into focal event-, time-, and activity-based PM) and the WM tests. The results showed that the two groups exhibited similar focal event-, time-, and activity-based PM performance. Although age and gender did not modulate the effect of implementation intentions on PM, WM capacity moderated the implementation intention effect on time-based PM. Specifically, higher WM capacity predicted higher implementation intention benefit. These findings suggest that children with higher WM capacity may have higher chance to benefit from the implementation intention strategy.