北京市為解決嚴重的道路堵塞問題，自2010年12月23日實施汽車限購政策。北京市於2010年10月傳出將要實施汽車限購政策，而本研究使用差中差方法估計消息傳出至開始實施日期間，政策消息對於汽車銷售量之影響。 研究中所使用之汽車銷售資料來源為中國「車輛登記管理所」中的「全中國登錄各月新增車輛」，以及「太平洋汽車網」的汽車詳細特性資料整理而成。以北京市為實驗組，其他非北京城市，與重慶市、天津市等為對照組，在控制了汽車特性以及加入了時間趨勢之後，可從實證結果得知，不論是以哪些城市當作對照組，在這段期間內，北京市的汽車銷售量皆有顯著的增加，與預測的結果相符。 在研究最後進一步使用穩定性檢驗，證明北京市汽車銷售量的突然增加是否真的為政策消息影響。最後結果亦與預期相符，證實北京市的汽車銷售量突然增加是由汽車限購政策消息所影響。 / To solve the serious road congestion problems, Beijing has implemented the restrictions on car ownership. In October, 2010, news started to spread that Beijing would bring the automobile purchase limit policy into practice. This study, using a method named “difference-in-difference”, estimated the policy’s impact on automobile sales volume in the period from when the news was launched to the day the policy was actually implemented. The data in this paper come from “Monthly Increase in Registered Vehicles Across China” of “Vehicle Registration and Management Bureau of China”, and the detailed characteristic data of vehicles from “Pacific Automobile Network”. We set Beijing as the experimental group, and the non-Beijing cities such as Chongqing and Tianjin as the control group. After controlling the characteristics of vehicles and adding time trend, we can learn from the experimental result that no matter which city is used as the control group, during the period, the vehicle sales volumes in Beijing increase significantly, which meets our expectation. In the last step of the research, stability test is used to prove whether the sudden increase of Beijing’s automobile sales volume is affected by the spread news. And the final result is also in accord with our expectation: the sudden increase in Beijing’s automobile sales volume is affected by the spread news of the automobile purchase limit policy.