By using different aerated materials to improve the pore characteristics of aerated concrete samples， and based on MATLAB platform， cross sectional images of the samples were processed to characterize their pore characteristics， and those samples were characterized by mass loss and compressive strength loss test after thawing， the influence of pore characteristics on the mechanical properties and frost resistance of aerated concrete were analyzed. Studies have shown that the method of sectional photograph with MATLAB could be used to collect and analyze the data of cross sectional images， and characterize different pore information； the sample with Al powder and entraining agent could reach the test standard of wall materials on freeze thaw cycle experiments； as the number of communication pore， the average pore size and the loose structure made of hydration increase， the water absorption of the samples increases， after 15 times freeze thaw cycles， the loss ratio of samples mass and compressive strength increase.