Abstract: Ore samples' proportioning and blending are the basis of ore dressing and smelting test, the rationality of which has a marked effect on final test results. The paper discusses the principles, procedures and formulas for samples' proportioning and blending of ores to be tested. A reasonable procedure including five steps is suggested as following: reviewing of geological report and sampling record, process mineralogy study, proportioning calculation, sample blending, and sample evaluation. It is worth noting that the incorporation of different ores in final sample should be in proportion to their representatives of mineral reserves respectively. And he prepared samples should represente the characters of ores in ore body, particularly in grades, mineral compositions, size distributions and without external pollution, because fully blending of samples is a key to avoid sampling error. The paper also introduces variance analysis for homogeneity testing of prepared samples.