This research has addressed the easiness of escape as one of the factors to affect the possibility of crime within a certain area of the urban space, and proposed an escape coefficient as a means to quantitatively identify the easiness of escape. The escape efficiency refers to the number of nodes to which a certain node can reach within a limited time. If the escape efficiency is high, the number of nodes that can be reached to within a limited time would exist, which means it would be easier for criminals to escape, thus raising the probability of crime occurrence. The proposed escape coefficient allowed the probability of crime within a certain area of the urban space to be quantified. Furthermore, this research showed that specific changes to the urban spatial structure can adjust the escape coefficient, thereby controling the probability of crime occurrence.