The study aimed to investigate the cognitive processing of prospective memory (PM) in patients with schizophrenia spectrum disorders (SSDs) by using an eye-tracking paradigm. In addition, the facilitating effects of prosocial intention (the desire to help others) on PM in SSDs were also examined. In phase 1, 26 patients (group1) and 25 healthy controls (HCs) were compared in an eye-tracking PM paradigm in terms of the PM accuracy and eye-tracking indices. In phase 2, 21 more patients (group2) were recruited, and a prosocial intention was introduced in the eye-tracking PM paradigm. Their PM accuracy and eye-tracking indices were compared with those in group1. The PM cue monitoring was indicated by the total fixation counts and fixation time on distractor words. In phase 1, group1 showed lower PM accuracy, fewer fixation counts and less fixation time on distractor words than HCs. In phase 2, group2 (with prosocial intention) performed significantly better than group1 (with typical instruction) on both PM accuracy and fixation time on distractor words. In both groups of SSDs, the PM accuracy was significantly correlated with both the fixation counts and the fixation time of distractor words. After controlling for the cue monitoring indices, the difference in PM accuracy remained significant between group1 and HCs but disappeared between group1 and group2. The cue monitoring deficit contributes to the PM impairment in SSDs. The facilitating effect of prosocial intention disappears after the control of cue monitoring, also indicating its critical role in PM.