Microencapsulated phase change material （mPCM） possess an excellent heat storage capacity， which can mitigate temperature fluctuation of soil during freezing/thawing in seasonal frozen ground. Two types of mPCM with butyl stearate， paraffin as the core material （B-PCM and P-PCM， respectively） and SiO₂ as shell material are evaluated using Scanning electron microscopy， X-ray photoelectron spectroscopy， Fourier transform infra-red spectroscopy and Thermal analysis， the effects of 4%， 8%， and 10% of mPCM on the frost heave characteristics of the silty clay in Lanzhou are studied through the freeze-thaw process and frost heave tests. The results show that the latent heat released by mPCM in the phase change process provides the soil with a thermal insulation effect， and the elapsed time required for the soil containing mPCM with 10% addition to drop from -10 ℃ to 10 ℃ is extended by 71.8%. The frost heave deformation， freezing depth and water content change rate of the soil decrease with the increase of mPCM concentrations； and the differences in core-to-shell ratio between B-PCM and P-PCM leads to different trends in the extent of water migration after frost heave. In general， the positive effect of mPCM on the soil is manifested in improving the thermal insulation performance of the soil， inhibiting frost heave deformation， etc. However， adding more than 8% mPCM will increase the frost heave of the superficial layer of the soil， which is related to the water absorption of the SiO₂ shell material.