On the base of gases molecular and kinetic theory a mathematical model of interaction between powder particles and plasma jet is developed. Three-dimensional description of plasma forming gas density distribution as well as particle motion in the plasma jet are a characteristic property of the model. A software for practical realization of the mathematical model is created. Said software provides the possibility to investigate an effect of low-pressure plasma spraying parameters on particle velocity andco-ordinates in the plasma jet. Computer simulation of particle velocity for powders from aluminium and tungsten oxides in argon plasma under 60 Mbar is conducted. A "Plasma-Tecbnik" VPS unit is used for testing the developed model. Particle velocity measurement is made by a specially developed optical-electronic unit.