Belt conveyor is widely used in mine, coal, chemical industry, ports, and power plants. It’s one of the significant devices of continuous conveyor. Roller is a crucial component with regard to belt conveyor system, which supports belts and cargos. In the design of the belt conveyor, a third of major consumption went into rollers. The critical consideration for minimum cost, which including operating, manufacturing, maintenance expenditure, is the selection of idler spacing. For optimization purposes, the optimum pitch between the rollers is regard as more decisive variable, especially for minimizing consumption and reducing rollers’ number than other various factors. This paper discusses the idler spacing to proceed from original technical first, secondly analyzes the effective factors in detail and then deduces rational arrangement mathematical expressions of idler spacing. Simultaneously, combining with the corresponding parameter, we draw up the hierarchical layout figure of idler spacing distribution through the calculation expression. It’s the optimal option of idler spacing that providing an outstanding reference in the actual production.