The electrolytic Al-Si-Ti alloy （AST） and the electrolytic low Ti aluminum base alloy （LTA） were produced by two methods in the industrial electrolytic tank. SE（B） specimens of ZL101A alloy obtained by above two alloys have been prepared to observe the fatigue crack propagation of the AST alloy and LTA alloy. Two key parameters in the Paris formula and critical value can be given by fitting representative data points in one set data obtained by testing fatigue crack propagation rate on a MTS 810 material machine. The results show that compared with ZL101A alloy prepared by AST, the ZL101A alloy prepared by LTA exhibits better anti-fatigue crack propagation behavior, which is attributed to higher Fe content in AST alloy deteriorating the anti-fatigue crack propagation. Therefore, either decreasing Fe content or modifying Fe in the AST alloy can improve the anti-fatigue crack propagation behavior of AST alloy.