As to whether there exists middle voice in Mandarin and what is the middle-voice structure in Mandarin, many debates are involved in. However, in these arguments, Mandarin is always compared to the so-called middle voice in English and German etc. Therefore, there is such viewpoint that ‘all middle-voice constructions should have typical transitive verbs and no agent as subject. Thereby the middle-voice in Mandarin should be of the form (2), which seems to be similar to (1) in English:
（1）The book reads easily. （2）这本书读起来很容易。
In fact, (2) is not a typical middle-voice, and the characteristics of middle voice should not be restricted to only these two points. If the distinction between the middle voice and active, passive is that middle voice has semantic agent which can't be realized syntactically, then under which circumstance may the constructions which have no agent originally introduce a semantically agentive constituent? Furthermore, if the distinction between middle voice and active, passive is that there is no agentive subject of the transitive verb, then in what structure transitive verbs can't or needn't require agentive subjects. Sentences below are likely more typical middle-voice:
（3）a.孩子给病了 b. 这件事难办 c. 米饭煮糊了
If the above analysis is solid, the Transitivity system of verbs can be reconstructed. In the new framework, the overall structure of verbs can be divided into two layers, one is the inner layer, in which each verb has only one internal argument, such as ergative and middle-voice; the other is the outer layer, such as active and passive. Ergative and middle voice both have no external arguments, but only internal arguments, which are all themes. The distinction between ergative and middle voice is that the former has no external argument in both syntax and semantics, but the middle voice has semantic external argument, which has no corresponding syntactic slot. As is mentioned above, there might be some morpho syntactic markers for ergative and middle voice respectively. Furthermore, when the inner layer is embedded into the outer layer, the passive and active with the syntactic slot of external argument, namely, the agent, can be constructed.