A coplanar electrode photodiode array and a manufacturing method thereof are disclosed. On a top side of a low resistance rate substrate, a high resistance epitaxial silicon wafer, a first conductive type heavily doped region and a second conductive type doped region are formed, which are a cathode and an anode of a photodiode respectively. The structure includes a trench structure formed between the anode and the cathode, the trench structure may be form by a gap, an insulating material, a conductive structure, a reflective material, and ion implantation, and also includes a first conductive type heavily doped region, an insulating isolation layer or a conductive structure with an insulating layer, and the like formed under the anode and the cathode.