Breakage distribution and rate functions are important when using the population balance model (PBM) to simulate the grinding process. To get the breakage distribution of diasporic bauxite, laboratory tests were carried out. Non-first order breakage with different deceleration rates for different size intervals is found, which is most probably caused by the heterogeneity of the ore. A method to describe the non-first order breakage is then proposed based on the test results. In the method, non-first order breakage is firstly described using piecewise linearization method in which grinding time is divided into several pieces and breakage is assumed to be first order in each piece. So, the breakage rates are calculated by taking the product of the last piece as feed and then established as a function of particle size and grinding time. Based on the predetermined breakage rate function, the breakage distribution of the ore is back-calculated from the experimental data using the PBM. Finally, the obtained breakage parameters are validated and the simulated data are in good agreement with the experimental data. The obtained breakage distribution and the method for breakage rate description are both bases for modlling the full scale ball milling process of bauxite.