中文摘要：

文章利用江苏省“十五”期问的面板数据对警力与犯罪问题进行实证研究。与以往文献不同，我们把一线民警从整体警力中剥离出来，认为一线民警的数量与犯罪率存在双向因果关系。通过对联立方程组进行三阶段最小二乘估计（3SLS），我们发现，刑事案件以及治安案件案发数对一线民警比重没有显著的影响；增加一线民警比重能够显著减少刑事案件相对数，而对治安案件却没有显著影响；此外，警察总量对刑事案件以及治安案件的发生都没有显著影响。进一步研究发现，在经济社会环境不同的地区（例如苏南、苏北），尽管案发绝对数存在显著差异，但是警力与犯罪的相互关系并没有表现出显著的差异。

英文摘要：

This paper is an empirical research about the relationship between police and crime by using the panel data of Jiangsu Province from 2001-2005. Different from existed literature, we assume there are causal relationship between the no. of front line police （part of total police） and crin, e. We also assume the total no. of police is exogenous. The 3SLS method has been used to estimate the simultaneous model. Our conclusion is that： Neither the variation of the no. of the criminal crime nor the public security crime has significant effect on the variation of the front line police. In contrast, the increase of the proportion of the front line police will significantly reduce the criminal crime. We also find that the total no. of police don＇t have significant effect either on criminal cases or on public security cases. Further study shows that the mutual relationships between police and crime don＇t have significant difference in different regions of economic and social environment.