Finding highly efficient photocatalysts has practical significance for antibiotics degradation. In this work, g-C3N4 modified Ag3PO4 had been prepared via in-situ deposition method. Their photocatalytic activities were investigated through tetracycline hydrochloride (TCH) degradation under visible light. In summary, sample 6 wt% g-C3N4/Ag3PO4 (6 wt% CN/APO) exhibited a good degradation efficiency (72.1 %) to TCH within 30 min, while pure Ag3PO4 and g-C3N4 was only 57.4 % and 5.8 %, respectively. Because of the construction of heterojunction structure, 6 wt% CN/APO composite had low fluorescence intensity, high photocurrent density and low resistance, which were helpful for the rapid separation of photogenerated carriers. Therefore, the photocatalytic property of Ag3PO4 was obviously enhanced. In addition, sample 6 wt% CN/APO also showed excellent photocatalytic stability, and h+ played a main role in TCH degradation. Its possible photocatalytic mechanism was also elucidated.