Spray process of hydroxyapatite was optimized by an advanced statistical planning of experiments. Full factorial design of 24 experiments was used to find effects of four principal plasma spray parameters, i.e. electric power, plasma forming gas composition, carrier gas flow rate and distance of spraying onto microstructure of hydroxyapatite (HA) coatings and powders. The Nemrod software has been applied to obtain the mathematical model of influence of these parameters onto experimental response. The chosen response was the volume fraction of HA crystal phase with regard to its decomposition phases. Two most important factors influencing this response are electric power supplied to torch and art of powder injection. The crystal phase content of powders and coatings was determined using X–ray diffraction (XRD) quantitative analysis. The morphologies of coatings surfaces, cross sections were characterized using scanning electron microscope (SEM).