Abstract: In the alpine area with altitude of 3762 m,two cushion species,compact type cushion Thylacospermum caespitosum (Primulaceae) and loose type cushion Ceratoides compacta (Chenopodiaceae) were chosen as target species,the changes of soil microenvironment under two cushion species were studied. Nine individuals with 50 cm diameter of each cushion species were chosen,at the same time,nine open areas in same diameter without cushion growth were also chosen as controls,and sampled in their centers. The nutrients,physical structure,water content and temperature of soil under each selected cushions were determined,and were compared with those of open area without cushions. The results showed that both cushions improved the soil nutrients under their canopies,organic matter,total nitrogen,available nitrogen,available phosphorus and available potassium content in the soil beneath T. caespitosum was increased 27.91%(P>0.05),12.02%(P>0.05),107.38%(P<0.01),63.74%(P<0.01) and 22.36%(P<0.01),especially,compared with control. The available phosphorus,total phosphorus,available nitrogen,available potassium and total potassium content in the soil beneath C. compacta was increased 12.24%(P>0.05),3.68%(P>0.05),55.42%(P<0.05),4.6%(P<0.05) and 2.89%(P<0.05),especially,compared with control. Meanwhile,both cushions changed the physical structure of soil under their canopies,compared with open areas,soil bulk density under T. caespitosum and C. compacta was decreased 15.34% and 7.45% respectively,and noncapillary porosity,capillary porosity,total porosity and aeration porosity were increased 87.73% and 60.04%,29.79% and 15.40%,34.04% and 20.37%,80.55% and 54.80%,respectively. In addition,both cushions improved the water condition of soil beneath them,pondage was improved most,which was improved 87.73% by T. caespitosum and 60.04% by C. compacta. Soil water content was not increased much,which was increased 14.76% by T. caespitosum and 3.66% by C. compacta. Moreover,two cushion species maintained relatively constant temperature environments under their canopies,they increased the extreme low temperature and decreased the extreme high temperature of soil beneath them,and made the soil temperature under their canopies not to change much during a day. Comparison studied showed that the modification effects on soil microenvironment of the compact type cushion was much better than that of loose type cushion,this indicated that the compact canopy was more beneficial to the modification effects.