Photocatalytic CO2 reduction mimics natural photosynthesis, which is a potential technology for "carbon neutrality". This article will review the recent research progress of a class of distinguished photocatalytic CO2 reduction systems based on ZnS nanocrystal photocatalysts. We will focus on the pathway of maximizing the photoreduction rate of CO2 by continuously optimizing the catalyst design and the composition of the reaction medium. Such discussions will be meaningful and beneficial for developing universal strategies of solar fuel production. Finally, an outlook will be provided to brighten the prospects of ZnS-based photocatalytic CO2 reduction systems.