Objective:The legal medical experts usuallycalculate the area ofinjured organs in bodyor other injured items bycountingthe grids in coordination paper.The experiences of the legal medical experts determine the result of this method.The result is subjective and has serious errors.So it is not conductive to the court and case detection.Methods:This paper proposes a method to calculate the injured area by hybrid of K-means algorithm and region growing algorithm.Results:The experiment shows this method is effective to calculate the area of irregular region.Conclusion:The result of this method is more accurate than the method of counting the grids in coordination paper.