Prospective memory (PM) refers to remembering to do something at a future time. Studies have shown that implementation intention can improve PM performance. The present study aimed to examine the effect and mechanism of implementation intention on PM in individuals prone for schizotypal personality disorder (SPD proneness) in a laboratory condition. A total of 51 participants with SPD proneness and 51 controls were administered a PM task. They were further randomly assigned to an implementation intention condition and a typical instruction condition. All participants completed the PM task with low and high cognitive load conditions. The results showed that implementation intention improved PM performances in both SPD prone and control groups, indicating that implementation intention was an effective strategy for improving PM performance. However, the mechanisms were different for the two groups. For controls, implementation intention did not affect their cognitive resources allocation strategy. Participants with SPD proneness allocated significantly more cognitive resources to the PM task in the implementation intention condition.