Abstract: According to the high cost of twice stripping problem of the parallel mine, it put forward side-slope and inner dump inverted triangle and side-slope horizontal ditch diagram. Aiming at the side-slope horizo4ntal ditch diagram, the cubics function about dumping ditch depth is set up by the second stripping cost reduction, capacity decreases cost recruitment and transportation cost recruitment. Through the case study, we can see that the optimal selection of reasonable depth of groove can make the economic effect of the triangle coal mining in the mining area