X-type swirl pressure nozzle is a new type of nozzle with the spin core structure. Due to its superior atomization characteristics, it has been widely applied in the field of spraying dust suppression in recent years. Sauter mean diameter (hereinafter referred to as SMD) is an important indicator to evaluate the atomization characteristics and dust suppression performance of nozzles. In order to build the SMD prediction model for this type of nozzles, based on the independently designed spray experiment platform, the interaction law between the nozzle SMD and the four influence factors is obtained through the orthogonal design method. On this basis, a mathematical model for predicting the nozzle SMD is built using the multivariate nonlinear regression method. The results show that SMD increases with the increase of axial distance, absolute radial distance value and nozzle diameter, but decreases with the increase of feed water pressure. The primary and secondary sequence of the four factors affecting SMD is: feed water pressure > axial distance > nozzle diameter > radial distance. The fitting values of the multivariate nonlinear regression model are basically the same with the experimental values, with the relative error of less than 3.50% and the average relative error of only 1.35%, which can be used for the theoretical calculation of the SMD of the X-type swirl pressure nozzles. The multivariate nonlinear prediction model built in this study can provide guidance for the design and selection of such spraying dust suppression schemes as nozzle outlet diameter, feed water pressure and nozzle layout, etc. for the field engineering application of such nozzles. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.