The jamming performance of DIRCM is studied,and the power density on the target′s IRFPA(infrared focal plane array) and the tolerance angle of system′s irradiating are regarded as two indexes to evaluate the DIRCM′s jamming performance. Considering the influence of the diffraction effect in the atmospheric transmittance and the beam divergence angle from turbulence effect on the power density of target′s IRFPA,the jamming model of DIRCM was established,and the power density of target′s IRFPA from DIRCM′s irradiating beam was simulated. Then the tolerance angle model of DIRCM′s irradiating was established based on the concept of confidence interval. By simulating the two models,influences of irradiating distance,turbulence intensity and beam irradiating caliber on the power density of the target′s IRFPA and the tolerance angle of system are analyzed quantitatively.