Abstract: Some testings were done under different conditions of environmental erosion, including water and chemical solutions with different concentrations and pH values, to simulate the erosion effect on the cement-mixed soil of which the mixing ratio is specified and the specimens were sampled from the silty clay soil about 3 m deep under a roadbed. The test of unconfined compression strength of cement-mixed soil was carried out with the specimens cured for 90 days. A conclusion showed that the strength of cement-mixed soil decreased in acid and high strength solutions. On the contrary, strength increased evidently in alkaline environment. Therefore, the design formula of upright bearing capacity of cement-mixed soil pile is modified due to environmental erosion, and a coefficient named environmental effect factor is proposed with its range of value discussed.