Trajectory privacy protection schemes based on suppression strategies rarely take geospatial constraints into account, which is made more likely for an attacker to determine the user's true sensitive location and trajectory. To solve this problem, this paper presents a privacy budget allocation method based on privacy security level(PSL). Firstly, in a custom map, the idea of P-series is contributed to allocate a given total privacy budget reasonably to the initially sensitive locations. Then, the size of privacy security level for sensitive locations is dynamically adjusted by comparing it with the customized initial level threshold parameter μ. Finally, the privacy budget of the initial sensitive location is allocated to its neighbors based on the relationship between distance and degree between nodes. By comparing the PSL algorithm with the traditional allocation methods, the results show that it is more flexible to allocate a privacy budget without compromising location privacy under the same preset conditions.