In order to study early strength evolution of saturated SBS modified asphalt mixture， a mechanical model based on effect of stress concentration at circular hole was proposed， and the pore-edge stress of non-saturated and saturated pore was calculated respectively. Moisture induced susceptibility test and immersion test were carried out for asphalt mixture with different asphalt contents. Then indirect tension test was utilized to obtain the indirect tensile strength and tensile strength ratio. The results show that under the splitting load， the pore water pressure dissipates the stress concentration phenomenon of the weak pore. With the increase of the moisture induced susceptibility test cycle times and the bath time， the indirect tensile strength first decreases and then increases， and the tensile strength ratio continues to increase. The strength of the asphalt mixture in the process of moisture conditioning increases， because the sum of asphalt mixture strength and pore water pressure is collected together in fact. The influence of temperature on the strength of asphalt mixture is more significant than that of pore water pressure.