The invention discloses a novel GaN ultraviolet detector with a grid-control PIN structure and a preparation method of the novel GaN ultraviolet detector. The preparation method comprises the following steps that: 1) a GaN buffer layer and an n-type doped GaN layer are sequentially grown on a substrate; 2) an intrinsically doped GaN layer is grown on the n-type doped GaN layer; 3) a p-type doped AlGaN layer is grown on the intrinsically doped GaN layer; 4) an epitaxial layer material is selectively etched, so that an etched mesa and double steps can be formed; 5) a passivation layer is deposited on the mesa and the double steps; and 6) the passivation layer is etched, so that electrode holes can be formed, and metal electrodes are deposited. According to the novel GaN ultraviolet detectorwith the grid-control PIN structure of the invention, based on the PIN structure, rapid, accurate and high-sensitivity ultraviolet light detection can be realized; the influence of two-dimensional electron gas at a AlGaN/GaN heterogeneous interface can be suppressed or eliminated through a voltage applied by a side grid structure; and therefore, the detector is an ideal PIN structure detector. Theperformance such as the response speed, detection rate and sensitivity of the detector can be improved.