Merger &Acquisition is a way to allocate resources in the capital market, and also a way for enterprises to expand scale. Since the real estate industry has a prominent position in the national economy, and M&A events in the real estate industry are also increasing year by year, it is worth studying whether M&A can improve the performance of M&A enterprises. From the perspective of horizontal M&A of real estate enterprises, this paper studies whether the short-term and long-term performance of listed real estate enterprises can be improved under horizontal M&A. First, this paper studies the background of M&A, the performance of M&A and the motivation of M&A relate to the theory and analyzes development of the real estate industry in recent years. After that, this paper begins to conduct an empirical study on the short-term performance and the long-term performance of horizontal M&A of listed real estate enterprises. This paper selects the horizontal M&A of real estate enterprises occurred in 2016 as the research samples. The short-term research calculates the CAR of each day of the event window by using the method of event studying, and compares its change. The long-term research uses the method of factors studying to calculate the comprehensive performance score of each year before and after M&A. The research result of this paper shows that although horizontal M&A of real estate companies brings positive cumulative abnormal return in the short term, the CAR is very small. In the long term, the comprehensive performance scores of horizontal M&A of real estate companies decline and then rise slowly before and after M&A. Besides, in this paper, starting from the features of the real estate industry, I analysis the driving factors of M&A of the real estate and build the M &A performance evaluation system of real estate enterprises. Using the case method, with the help of the M&A performance evaluation system, this paper analyzed the performance of Chinese real estate enterprises-Vanke after M&A from short-term and long-term performance, finding out the factors to drive the improvement of performance of vanke through M&A. According to the analysis of the case, a series of suggestions are proposed from internal and external to improve performance of real estate enterprise after M&A of our country.Finally, this paper puts forward some suggestions to the participants of M&A. For example, listed real estate enterprises should pay attention to the cost of M&A and resource integration; Government departments should pay attention to marketization; Intermediary agent should be diligent and responsible. / Business Administration/Finance