Solar energy absorption and photo-induced charge separation and transfer are crucial to enhance photocatalytic properties. Here, the structural, electronic and photocatalytic properties of graphene quantum dots (GQDs), pure and O, N, S-v-modified MoS2 monolayers, GQDs-based heterostructures have been studied by theoretical calculations based on density functional theory. Compared with the GQDs, the obvious red shifts of the absorption peaks can be observed, the absorption intensities increases evidently, and the typical type-II band alignments can be formed after the construction of the pure, O, N, S-v-MoS2/GQDs heterostructures, which is beneficial to promote photo-induced charge transfer and more visible light harvesting. Subsequently, it is worth mentioning that N-MoS2/GQDs heterostructure also has the lower binding energy and higher absorption in the infrared region and impactful photo-induced electron injection from GQDs to N-MoS2 surface. Therefore, this work provides an instrumental and promising approach in designing new GQDs-based heterostructures to enhance the solar energy absorption and conversion.