[en] The thermal ablation rate and mass ablation rate of cured E-51 epoxy under long pulse laser irradiation were studied. The effects of irradiation time, maximum power density, frequency and pulse width were discussed. The thermal ablation rate gradually increased along with the irradiation time, and then reached a certain value. The effects of frequency and pulse width were little. With the maximum power density increasing, the thermal ablation rate rose first obviously and then the thermal ablation rate approached to a definite value. With a fixed maximum power density, the thermal ablation rate was certain and the mass ablation rate was directly proportional to laser frequency and pulse width. The results were verified according to the optical property, surface morphology and surface temperature in irradiation area of cured epoxy. (authors)