To better utilize carbon dots (CDs) as efficient photocatalysts, an excellent strategy of constructing CDs@MoS2 heterostructure is presented. Here a facile sonication-hydrothermal method is utilized to synthesize CDs@MoS2. Such heterostructure regulates the energy level configuration, and visible light absorption and the separation and transfer of photogenerated charges are enhanced remarkably, which is propitious for the production of more photoinduced charges and improvement of the heterogeneous photocatalytic activity. Meanwhile, the photocatalytic performance of CDs@MoS2 was obviously improved in methylene blue degradation. On the basis of a series of contrast experiments, the possible mechanism of the photocatalytic reaction is proposed. Therefore, this work offers a facile route for the design of a zero-dimensional/two-dimensional heterojunction for the adjustment of the energy level structure and the improvement in photocatalytic performance.