[Objective] Wind speeds at different slope positions of Haloxylon Ammodendron forest were investigated on the northeast edge of Ulan Buh desert, in order to reveal the variation of windbreak effectiveness of Haloxylon ammodendron with plantation age and spatial pattern.[Methods] Forests of H. ammodendron at 3 a, 5 a and 8 a plantation ages were selected as research objects. The wind speeds at 10 cm, 20 cm, 50 cm, 100 cm, 200 cm heights above ground were measured respectively in the bottom, middle and top of windward slope and bottom of leeward slope for windbreak effectiveness analyzing.[Results] The wind speed near ground surface declined with the increase of plantation ages. Windbreak effectiveness of 3 years' shrub was mainly found in 0-100 cm height, the averaged value was 48.19%. At 100-200 cm height, wind speed rebounded to the CK value quickly. Good windbreak effect were found both in 5 years and 8 years forests at height 0-200 cm, and their windbreak efficiency were 69.72% and 71.93% respectively. Correlation analysis showed that there existed a significant correlation between plantation pattern and windbreak effect. The correlation coefficients between windbreak effect and forest coverage, height and crown width were 0.935, 0.930, 0.942 respectively.[Conclusion] Windbreak effects in the bottom of windward slope and leeward slope were better than those in the middle and top of windward slope of 3 years forest. It was contrary for the forests having 5 years and 8 years plantation ages.