Abstract: In order to manage virtual memory of applications. The locality principle is a fundamental for performance optimization methods such as caching and prefetching. The strength of locality is described in a qualitative way as strong or weak at present. To evaluate the locality strength in a more accurate way, this paper proposes quantitative definitions and approaches of temporal and spatial locality strength respectively. The time complexity of this approach method is acceptable, and the quantitative locality strengths represent the behavior of running program precisely.