To simulate the degradation of cast-in-situ piles exposed to sulfate saline soil environments, a corrosion experiment of cast-in-situ specimen was conducted. The deterioration mechanism of fresh concrete specimen was studied. The difference of deterioration mechanism between precast concrete specimen and fresh concrete specimen was analyzed with comparison experiments. The effect of watercement ratio and concentration of sulfate solution on the durability of cast-in-situ concrete specimen was analyzed. The mass change rate and the relative value of compressive strength were used to quantify the degradation rule of fresh concrete specimen. The results show that both the concrete mass and the compressive strength increases firstly and then decreases. In the same condition, the fresh concrete specimen is the first to show the mass and compressive strength loss. The loss rate is 0.4% and 15%, respectively. The increase of sulfate concentration has not obvious effect on the degradation law of the fresh concrete specimen. However, with the watercement ratio increases, the fresh concrete specimen is prone to deterioration.