Series of large scaled model test has been carried out to examine the reinforcement mechanism of deep buried piles. Testing tools including rigid load cells, the earth pressure cells and data collecting systems are employed to measure the anti-thrust received by deep buried piles and the slope thrust of the slope on piles top. On the basis of the variation process of measured data, the time and the location of slide surface in the slope is determined, and the maximal anti-sliding force upward to the piles top could be gained by the data of earth pressure cells. Then the failure form process is analyzed with the anti-sliding length of the piles changed. The relationship between the sliding force received by the piles and that supplied by the slope on piles top is analyzed to supply scientific demonstration for the design method of slope reinforced by the deeply buried piles.