This research focused on the verb ‘Yu’, investigates from a synchronic and diachronic perspective, analyzes the characteristics of the basic meaning represented by the meanings of ‘give’ and ‘socialize with sb’. and the development and changes of semantics, and demonstrates them through diagrams. And also analyzeds the semantic relationship between the semantic items of the verb ‘Yu’. Through the investigation of the semantic relationship, we can give an explanation tha why the meaning of ‘Yu’ in the meaning of ‘together’ can be explained to ‘help’, ‘give’, ‘applaud’ and ‘socialize with sb.’ We think the result breaks through the limitations of previous research. This research also pays attention to the expansion of the semantic function of the verb ‘Yu’, especially the ‘introduce tool’ function and the “passive” function. Regarding the function of ‘introduce tool’, this article refers to the formula of “COMITATIVE tool case INSTRUMENT” in linguistic typology, and sorts out the meaning of ‘Yu’ from ‘accompany’ to ‘attachment’ and then to ‘utilization’, and at last develop to the ‘introduce tool’ function. Regarding the “passive” function, after specific analysis, the conclusion is that the “passive” function of ‘Yu’ comes from two development paths, one is induced by the meaning of ‘give’, and the other is induced by the meaning of ‘accompany’. The common point of the ‘passive’ function is that they have experienced ‘causative’ in the previous stage of passivity. The difference is that the ‘causative’ of the former approach comes from ‘give’, but the source of the latter way comes from ‘accompany’.