How to assess the accuracy of forest land patch (sub-compartment) delineation is a key point in many tasks of inspection and evaluation in forestry.Area accuracy was usually used as the only indicator to assess the quality of patch delineation,but it could not represent the accuracy of spatial positioning of the sub-compartment.Therefore,this paper analyzed the typical cases of patch borderline positioning,then defined the patch overlap rate used to represent the overlap between reference polygon and inventory polygon,and proposed its calculation method.Using the overlap rate together with the area accuracy,the accuracy of patch positioning could be evaluated much more accurately and objectively.A case study indicated that if the overlap rate is greater than 85%,the patch delineation could be recognized as qualified in forest management inventory.