Abstract: In the past 30 years,pipeline hydraulic transportation of the solid materials has been applied much more wildly. In the design of the pipeline hydraulic transportation system, the non-silting critical velocity is an important parameter needed to be ascertained at first, which has a great significance for the system operation safety. For the fine-grained materials in the pipeline hydraulic transportation system, many calculation methods can be applied for this parameter. However, for the coarse-grained materials, how to choose the calculation formulas is a difficult problem because of their great different results. In this paper, based on the comparison and analysis of the existing non-silting critical velocity calculation formulas, the influences of the factors including particle concentration, size distribution, density and diameter of the pipeline, on the non-silting critical velocity are discussed especially for the coarse-grained materials, the structure differences of the formulas are compared. A careful analysis of variation law of the non-silting critical velocity changed with the increase of particle size is made by sorting out the experimental data of the coarse-grained materials transport given by different scholars. And based on a dimensional analysis, a new formula to calculate the non-silting critical velocity in a horizontal pipeline hydraulic transportation system has been suggested. The relative errors between the calculated results and the tested data are less than 10%, which can basically meet engineering requirements of calculation of the non-silting critical velocity.