Taking the 140m spoil ground on the right side of K89+250 from Liupanshui to Weining expressway in Guizhou Province as research object, the drainage capacity, the stability of retaining wall and slope are evaluated by site investigation and calculation and the stability of the spoil ground is evaluated. The results show that the peak discharge of the spoil ground is 0.874 m3· s-1, which is less than the maximum discharge capacity of 1.95 m3· s-1of the drainage ditch. The local stability coefficient of the spoil ground slope is 1.404 and the overall stability coefficient is 1.360 under normal operating conditions. The local stability coefficient is 1.303 and the overall stability coefficient is 1.172 under abnormal operating conditions. Anti-sliding stability of the retaining wall is greater than 1.3, anti-overturning stability is greater than 1.5, and the base stress is less than 250 kPa of foundation bearing capacity. Consequently, dimensions of drainage ditches can meet the drainage requirements of the spoil ground. The overall and local stability of the spoil ground slope under different working conditions can meet the requirements of stability and safety, and the anti-sliding stability, anti-overturning stability and bearing capacity of retaining wall also can meet the requirements of stability and safety. It is recommended to plant grass on the slope to improve the interception and drainage of the spoil ground and reduce the soil erosion on the slope.