A heterostructure composed of spherical hollow WS₂ and petal-like MoS₂ was systematically studied. The results showed that the spherical hollow structures exposed more active sites, and the construction of heterostructures triggered the synergistic effect between WS₂ and MoS₂ and improved the hydrogen evolution reaction (HER) performances with better electron transfer ability. More importantly, the density functional theory calculations further clarified the synergistic mechanism, in which the MoS₂/WS₂ heterostructure could effectively regulate the hydrogen adsorption free energy to achieve the minimum value with a W/Mo atomic ratio of 2:25. Consequently, the optimized WMo-2/25 catalyst exhibited superior electrocatalytic HER activity with a low Tafel slope of 53 mV/dec as well as good durability.