Abstract: The investigation of GaN-based avalanche photodiodes(APDs) was motivated by the demand of high sensitivity ultraviolet detectors in numerous civilian and military applications. APDs operate under high reverse bias voltage, and carriers in the device caused impact ionization under high electric fields, as a result, the avalanche multiplication could be obtained. In this paper, reviews were made on the development of GaN-based avalanche photodiodes, the largest value of gain in this work was nearly 3105. Relationship between width of the intrinsic layer and dark current has been studied. The measuring system based on phase sensitive detecting technique has been shown. Relationships between modulating frequencies and noise has also been investigated. It was found that in the range of low frequency(30-2 kHz), the excess noise behaved as 1/f noise. In the end, the recent developments and applications of the Geiger mode operations of GaN-based APDs are introduced.