The invention relates to an infrared-transmitting high-sensitivity visible light detector and its preparation method. The detector is composed of passivation layer (14), upper electrode (13), heterojunction (15), lower electrode (3), and intrinsic monocrystalline silicon substrate (2). The upper electrode (13) is the material that is electrically conductive and transparent to visible light and infrared light. The heterojunction (15) is divided into heterojunction upper layer (5) and heterojunction lower layer (4), wherein the upper heterojunction layer (5) is a nano film sensitive to visible light and capable of transmitting infrared ray, and the lower heterojunction layer (4) is intrinsic monocrystalline silicon. When visible light and infrared light pass through the upper electrode (13) and the heterojunction upper layer (5), the visible light excites electron-hole pairs in the heterojunction (15), which are collected by the upper and lower electrodes and flow out through longitudinally arranged metal columns, while infrared light passes through the whole detection structure, so that visible light can be detected without affecting infrared transmission. The distance between the electrode and the junction zone is very small, which can reduce the recombination rate of electron-hole pairs before reaching the electrode and improve the collection efficiency of photo-generated carriers. The structural design of longitudinal metal reduces light shielding and improves sensitivity.