Based on a concept of average contact mesh probability a mathematic model of probability screen was established,which shows the quantitative relation between the operating parameters and screening efficiency.

This paper discuss a new searching method for submarine which have been found by other naval force and analyse it s searching efficency,at the same time we use three index-average finding probability,searching time and frenquency of change direction to emulate and compare with the expanding square matrix method being used in navy currently.