Abstract: The Triassic Jiucaiyuanzi Formation is one of the main hydrocarbon-bearing strata in Fudong slope area of Junggar basin.The lack of research on the types and characteristics of the diagenesis affected the recognition and development of the reservoirs.By using such testing technology as slice observation, SEM,property analysis, X-Ray and electron probe,the diagenesis characteristics and its effect on reservoir property were clarified.Results show that reservoir types of Jiucaiyuanzi formation are mainly middle pore and low permeability reservoirs,with some types being middle pore and middle-high permeability reservoirs. The reservoirs have strong micro anisotropy caused by diagenesis.It is concluded that the diagenesis of compaction,cementation and dissolution was developed in Jiucaiyuanzi formation.The diagenesis stage is in stage A.The moderatein tensity of the compaction is the key factors to poor property; the intensity of cementation is moderate-strong and the intensity of dissolution is weak-moderate, sometimes strong. Calcite, clay minerals and siliceous cementation further decreases the property of reservoirs, while zeolite cementation and its dissolution improves the property.