The aim of this paper is to make clear the concept of safety evaluation of urban area and to identify an urban safety evaluation function.

Firstly, the concepts on the urban safety level are analyzed. The definitions on a loss vector, a frequency function, a safety evaluation function, and a safety level are given.

Secondly, the formula on the relationship between the safety evaluation function and the preference of individuals are obtained Furthermore, the safety evaluation function are estimated through the survey of preference. By the criterion AIC, the most reasonable safety evaluation function is a first-order threshold type function.

^*1Dr. of Engineering. Deputy Head, Planning and Information Department,Building Research Institute.