In order to accurately determine effective hydraulic fracture length and its influencing factors of gas well,to improve the pertinence of hydraulic fracturing in Xujiahe Reservoir,West Sichuan,the relationship be-tween effective length obtained from the gas wells and propped length obtained from net pressure fitting is deter-mined.The degree of the parametersinfluence on effective length is analysed by grey correlation analysis theory, and its implication to fracturing design is also analysed.Calculation results showed that there is a noticeable cor-relativity between effective length and propped length (Le =0.0584 Lp1.3593 ),and effective length is shorter obvi-ously than propped length;construction parameters (especially fracturing fluid volume)is the primary determinant of effective length in Xujiahe Reservoir,and the stress difference between barrier and interbed is the key objective factor.This research provides a reference for post-fracturing evaluatio.