The hierarchical fragmentation of a molecular cloud is modelled as a random process by the Monte Carlo method. It is proposed that the IMF for stár formation is bimodal. The probability of the fragmentation in each mode is a function of the initial cloud mass and defined critical mass, which can be derived from the surface
density and temperature of cloud. The modelled IMF is compared with the empirically determined function and the best fit was found for critical masses of 0.3 M^ for low-mass mode and 2.0 M„ for
high-mass mode of star formation.