Abstract: The cohesion represents the tight degree of the components of a software module.In an object-oriented environment,the cohesion means the tight degree among the attributes and methods in a class.Based on the class dependence graph and structure entropy,a new method is proposed to measure the cohesion of a class.This method measures the cohesion between attributes and attributes,attributes and methods,methods and methods of a class.The proposed method provides a guideline for evaluating the cohesion of a class.