Аннотация:The accumulative regime of diamond graphitization by a sequence of sub-threshold (for single impulse) femtosecond laser pulses has been studied. The model describing accumulative graphitization as gradual growth of graphite centers embedded into a diamond matrix is presented. The experimental data suggest that both the laser heating of these centers and the direct photodamage of the diamond lattice are involved in the process of diamond-graphite transformation.