A femtosecond laser with wavelength of 800 nm was used to process the micro-pits array on the surface of carbide YG6. The change of ablation threshold and ablation diameter of carbide YG6 and its ablation mechanism under different energy density and pulse number were studied by optical profiler. The result of the test shows that the multi-pulse ablation threshold of carbide YG6 decreases with the increase of the pulses number and it shows a significant accumulation effect. The quantitative relationship among ablation threshold, ablation diameter, pulses number and central energy density of multi-pulse femtosecond laser processing YG6 was obtained. The multi-pulse ablation threshold of YG6 is mainly related to the number of pulses, which is determined by ablation threshold of single pulse and accumulation coefficient. The result of the test shows that the laser ablation threshold of YG6 is 1.14±0.06 J/cm2 and accumulation coefficient is 0.84±0.02. The ablation diameter is mainly related to the energy density and the number of pulses at the center, which is determined by the beam waist radius, the ablation threshold of single pulse and the accumulation coefficient. The YG6 was ablated by multi-group average power and pulse number, which verified the reliability of the ablation threshold of single pulse and accumulation coefficient.