The particle le in Mandarin has always been a hot topic as well as a difficult issue in Chinese grammar,and the controversy over the conclusion of this topic is often due to the different approaches and philosophies adopted by various scholars.In this paper,we propose the following principles on the research of le.First,at the beginning of the study,it is not appropriate to aim at finding a uniform meaning of le in all usages,because theoretically le may have more than one function and may not have a common semantic feature in all usages.Second,in semantic analysis,it is important to understand that a grammatical form that encodes the meaning s may not be used in all sentences that contain the meaning s.Third,a scheme for the semantic analysis of a grammatical form must be able to fully explain the use of that form.These claims may,to a certain extent,represent some of the methodological principles in the study of Chinese functional words.The paper also points out how to falsify the grammatical heterogeneity of the particle le in Mandarin.In a study,the conclusion is certainly worthy of attention,but the methodological principles and argumentative approaches are also important.We propose several principles for research on functional words.In the analysis of a functional form M,it is not appropriate to take any a-priori view on M;the right approach is to take into account all logical possibilities.Logically,M may be either single-functional and single-featured,or multi-functional and multi-featured.All uses of M may have a common meaning,but this is not a necessary case.The research should begin by examining a set of phenomena involving M one by one,and then sort out the overall distributional conditions of M.Then,based on these conditions,the semantic features of M can be described according to the principle of"form-meaning"mutual verification.The final conclusion on M must be able to predict all the usages of M as effectively as possible.This conclusion should also be kept simple and concise.Thus,we should try to unify the multiple uses of M into one semantic function,and reduce the multiple syntactic representations of M to one semantic feature.