在现实生活中，行为人由于精神紧张、忽视注意义务以及客观环境多变、现实情况复杂等诸多原因，对客观上并不存在的不法侵害发生了误认，基于主观上的“防卫意图”实施了明显超出必要限度的“防卫行为”，并造成无辜他人受损的现象却屡见不鲜，此即刑法理论上的“假想防卫过当”。由于假想防卫过当现象本身的复杂性和法律上没有明文规定，故在理论界和司法实践中一直争议颇大、分歧不断。本文结合司法实践中的困惑，对假想防卫过当的相关问题进行了详细具体的讨论，共分为三章。 第一章假想防卫过当概述部分，具体阐述了假想防卫过当的概念、性质、表现形式以及四个成立要件：首要要件——在客观上不法侵害并不存在，因行为人“假想”具有合理根据而对此发生误认；主观要件——在主观上行为人具有防卫意图；时间要件——假想的“不法侵害”须处于正在进行中；结果要件——“防卫行为”超出必要限度且造成重大损害。 第二章阐明了当前假想防卫过当处理面临的司法困惑，主要选取康某“赴鸿门宴杀假想敌”案与蔡某“见义勇为”案两个假想防卫过当案，具体分析了两案争议焦点皆在于被告人是否构成假想防卫及有无过当之嫌。 第三章作为本文的核心部分主要讨论了假想防卫过当的刑事责任认定问题，首先从理论联系司法实践的角度分析两案定性问题，以假想防卫过当成立四要件着手，充分论证了两案完全符合假想防卫过当的成立要件；其次，讨论假想防卫过当的罪过形式归根结底是要分析过当部分的罪过形式，认定行为人承担何种刑事责任也主要是对其自身防卫行为过限的认识状况决定的。其罪过形式排除直接故意，出于间接故意、过失与意外事件；在明确两案件定性及罪过形式后假想防卫过当如何处理的问题便可迎刃而解。

In real life, this phenomenon is not uncommon: due to mental stress, ignoring the attention obligation and the changing objective environment, the complex reality of the situation and many other reasons，in fact, the infringement does not objectively exist, but the perpetrator who based on the "defense of intent" implements the "defensive act" that exceeded the limits necessary and caused damage to innocent others. It is called excessive imaginary defense in our Criminal Law. Since there is no legal provision and the complexity of the phenomenon, excessive imaginary defense has been controversial in theory circle and judicial practice. In this paper, combined with the confusion in the judicial practice, the author discusses the problem of excessive imaginary in detail, and this paper is divided into three chapters. The first chapter is an overview of excessive imaginary defense; this paper specifically addressed the concept, nature, manifestations and five constituent components of excessive imaginary defense---- illegal violation does not exist objectively, imaginary "unlawful infringement" to be underway, the actor has subjective intention of defense, the actor’s "imagination" must have rational basis, "defensive behavior" exceed the limits necessary and cause damage to innocent others. The second chapter deals with the judicial confusion of excessive imaginary defense, mainly takes KangMou and CaiMou heroic the two cases as example to analyze the focus of controversy is that whether the defendant constitutes excessive imaginary defense. As the core part of this paper, the third chapter mainly discusses the problem of criminal liability in excessive imaginary defense. First of all, from theory with the perspective of judicial practice, and from the five-components of excessive imaginary defense constitution, the author fully demonstrates the two cases complied with the above five constituent components. Secondly, when we analyzes the subjective fault of excessive imaginary defense, we should analyzes the subjective fault of the part in exceeding the legitimate defense of the necessary limits, including do not contain direct intent, negligence and indirect intention, may be out of the accident. Besides, after classify the constituent components and subjective fault of excessive imaginary defense, the last problem on criminal liability’s identification will be solved.