In the process of fine reservoir description of the Gao-17 fault block, GaoQing oilfiled, we discovered crevasse channel microfacies, and then compared and analyzed its origin, sedimentary characteristics, depositional model, and spatial distribution. The crevasse channel is an extreme narrow and shallow short range small-size channel with fixed paths and specified metering function in wide interchannels of the fluvial-delta sedimentary system, and is formed after the main stream channel rip-up in the cataclysm period. The formation of the crevasse channel impacts the original main stream channel little. In contrast with the main stream channel, the crevasse channel presents features of fine-grained, poorly graded, high silt content, small bedding scale, weak erosion, a little normal cycle, a little bad reservoir nature, very thin sand body (<2.5m) and narrow (<100ｍ),etc. By means of analyzing sub-sea crevasse channel depositional mechanism, we established 4 depositional models including fading model, branching model, extreme fan model and affluxion model. Because the sub-sea crevasse channel is very narrow and discrete, it develops small and plenty remaining oil concentration sand body of uncontrollable well network or imperfect injector producer. And because the sand body scalar quantity is very large, reserves of remaining oil are extraordinary impressive.