Size distribution of nano-carbides produced by duplex treatments of surface nanocrystallization (by surface severe plastic deformation) and plasma electrolytic carburizing on CP-Ti was investigated. Skewness and kurtosis of Gussian shape distribution curves were studied and the effect of time was determined. The usage of longer time is more suitable for achieving less size of complex nano-carbides. Surface roughness of treated samples was measured. It is observed that there is an optimum level for time on surface roughness increasing (difference between two measured data).