分拆上市是指上市公司将其部分资产或业务进行分拆从而形成在法律、组织和经营上独立的子公司，并将子公司于金融市场首次公开募股的行为，由于其兼具再融资和资产重组的特征而在金融实务和学术研究上得到了广泛关注。出于对分拆上市可能带来的利益输送等问题的担忧，长期以来我国监管层对分拆上市持谨慎态度。2019年12月，我国证监会发布《上市公司分拆所属子公司境内上市试点若干规定》，放开了对“A拆A”的监管，引发了上市公司分拆上市的热潮。而我国市场分拆上市究竟会带来正公告效应还是负公告效应，以及公告效应理论上应该如何解释，目前还鲜有A股市场的相关研究证明。 本文首先对厦门钨业分拆子公司上市的案例进行研究，分析了厦门钨业分拆上市的背景与目的，联系理论定性地解释其分拆上市带来的市场反应。接着，本文对分拆上市的公告效应及其解释理论进行了实证上的研究与检验。本文使用2019年12月至2021年1月公布分拆子公司境内上市计划的56次分拆事件为样本，通过事件研究法证明了A股上市公司的分拆上市事件具有显著的正公告效应。在此基础上，本文使用横截面回归的方法对解释分拆上市公告效应的理论进行检验，证明分拆上市公告效应的大小与子公司相对母公司规模的大小呈正相关，与母子公司行业相关性呈负相关，从而支持了分拆上市的剥离收益理论和归核化战略理论而拒绝了信息不对称理论。

In an equity carve-out, a listed company splits some of its assets or businesses into a legally, organizationally, and operationally independent subsidiary, and sells a portion of its ownership in the subsidiary via an initial public offering in the financial market. Equity carve-outs have received extensive attention of financial practice and academics because they combine characteristics of both restructuring and financing transactions. Out of concerns about the illegal benefits transmission, Chinese regulator has long been cautious about equity carve-outs. In December 2019, the China Securities Regulatory Commission issued the “Regulations on Listed Companies’ Carve-outs”, which actually liberalized the supervision of equity carve-outs. As for whether the carve-out will bring about a positive announcement effect or the opposite, and how the announcement effect should be explained, there are still few relevant studies in Chinese stock market. This paper first studies the case of Xiamen Tungsten's equity carve-out, analyzes the background and purpose of the carve-out, and qualitatively explains the stock price reaction based on relevant theories. Next, this paper conducts empirical research on the announcement effect of carve-outs and its explaining theories. Using a sample of 56 carve-outs that occurred in the period of December 2019 to January 2021, the research shows that carve-outs in Chinese stock market bring about a significant positive announcement effect. On this basis, this paper uses the cross-sectional regression method to test the theories proposed to explain the positive stock price reaction. This study shows that the announcement effect is positively correlated with the relative size of the subsidiary and is negatively correlated with the relevance of parent-subsidiary industry characteristics, which supports the divestiture gains theory and the refocusing strategy theory, but rejects the asymmetric information theory.