Abstract: To calculate the weight of erosive ion influencing' mechanical property of cement-soil piles and find the quantification of these factors which corrode and weaken the strength of cement-soil piles, the theory of analytic hierarchy process(AHP) is introduced. System of hierarchical analysis is constructed and judgment matrix is made. Maximum eigenvalue of each factor is calculated with sum method. Finally consistency test is carried out and weight is calculated to receive reliable, accurate weight, providing theoretical reference for designing and constructing cement-soil pile composite foundation based on pollutant and erosive earth mass.