Bismuth telluride (Bi2Te3) is a typical topological insulator, which possesses a narrow band gap and exhibits fascinating performance in the photodetector field. In this work, we fabricated a Bi2Te3/graphene heterostructure via a facile one-pot hydrothermal method. The as-prepared composites were used as the electrode materials for the photoelectrochemical (PEC)-type photodetector. From the results of PEC tests, we obviously found that the Bi2Te3/graphene heterostructure offers a remarkable improvement in photoresponse compared to that of sole Bi2Te3, and effectively demonstrates effective photocarrier generation and transfer at the interface between the graphene and Bi2Te3, which can enhance the properties of the photoresponse. Moreover, owing to the self-powered ability of the PEC-type photodetector, it can work under the bias potential of 0 V and exhibits a prominent photoresponse which can reach 2.2 mA W-1. Also, the photocurrent density of the prepared Bi2Te3/graphene heterostructure-based photodetector can almost linearly rise with the increased irradiation power density. Even if the light intensity was reduced to 40 mW cm-2, the photocurrent density could also reach 67 μA cm-2, which ensures the photodetection ability of the as-prepared Bi2Te3/graphene under low light intensity. The excellent performance of a Bi2Te3/graphene heterostructure for a PEC-type photodetector holds great promise in the field of photoelectric detection.