Abstract: Based on analysis of lithology,physical porperties,pore feature,pore filling mineral composition and formation fluid in reservior C-2 in Hanqu oil field of northern Shaanxi,the authors discussed the main geological factors related to injury of reservior C-2 during exploration and exploitation.Organic dirt,acid sensitivity and water lock effect are the main factors caused injury of reservior C-2,and water sensitivity,velocity sensitivity and fluid property are the minor factors.As a result,some suggestions are proposed to avoid reservior injury during development,such as injection of wax proof agent,clay stabilzing agent and Fe 3+stabilizing agent etc.