Abstract: Since the probability distribution equations of broken ore displacement were revised and perfected, the stochastic theory of ore drawing has gained much improvement in both computing precision and popularity. This paper introduces in detail three of the probability distribution equations corresponding to ore drawing under infinite, semi-infinite and dip-wall boundaries in caving system. Three equations can all be fitted with Grassain Distribution Function, whose square deviations being expressed as σ²=1/2β_iz_i^α,where α_iβ_i broken ore flowing parameters. These equations not only are the basis of the stochastic theory, but also can be used to improve the computer simulation model of ore drawing.