The purpose of this paper is to find ways to distinguish Chinese dative prepositions ``wei(爲)``, ``bang(幇)``, ``ti(替)`` and ``gei(給)``by illustrating their actual usages and the differences of their functions through a comparative analysis based on the modern Chinese corpus. There are some prepositional groups whose members share a common meaning in modern Chinese. This paper will suggest ``synonymity`` for the members of each prepositional group, that is, the members of each prepositional group share a common meaning, but at the same time, they also represent their unique features individually. ``Synonymity`` usually appears in content word categories while the functional words, such as prepositions, are often polysemous, so the synonymity of prepositions will provide an interesting, in terms of the diversity of characteristics, of functional words. In connection with the synonymity of prepositions, this paper will discuss that lexical meaning acts as a standard of distinguishing synoymous prepositions. For the discussion about the influence of lexical meaning on the functional words, it will be suggested that there are some Chinese prepositions used as dative markers, such as ``wei(爲)``, ``bang(幇)``, ``ti(替)`` and ``gei(給)``, and show how to distinguish them by their lexical meaning. This paper is formed around the following discussions: (1) to investigate the frequency in use of ``wei(爲)``, ``bang(幇)``, ``ti(替)`` and ``gei(給)`` based on the modern Chinese corpus (2) to compare the features of wei(爲)/bang(幇)/ti(替)/gei(給)-constructions through comparing the types of their predicates and the semantic features of their predicates (3) to compare the semantic structure of wei(爲)/bang(幇)/ti(替)/gei(給)-constructions based on the real doers of the action represented by predicates (4) to discuss discourse functions of wei/bang(幇)/ti(替)/gei(給)-constructions from the perspective of polite strategy.