Abstract: At the southwestern margin of Ulan Buh Desert, several bare sand dunes with similar size and direction were selected, which were laid with PLA sand barrier and straw barrier. The designed specifications of the barriers were chosen as 1m×1m, 2m×2m, 3m×3m. The water content of surface soil protected with different barriers and on different slope positions were measured within 3 successive years since 2008. The long-term effects of PLA and straw sand barrier on the moisture content of surface soil were compared, while bare sand dune without laid barrier was chosen as control. The results showed that soil water content increased with time for both sand dunes protected with PLA or straw barrier and bare sand dunes, the increase of soil water content of protected sand dunes with two kinds of barriers was significantly larger than that of bare sand dunes. To maintain soil moisture for a long time, PLA sand barrier with size of 2m×2m performed the best effect. On sand dunes protected with PLA sand barriers, in 0-10cm depth the soil water contend in the windward slope was larger than that in leeward slope, which was in turn larger than that on slop top. In 10-20cm depth, the soil water contend on slop top was larger than that in the windward slope, which was in turn larger than that in leeward slope. However, on sand dunes protected with straw barriers, the tendency for two depths was reverse.