In order to obtain the high-power laser beam, the dichroic mirror was used to combine the two different types of pulse and continuous high energy laser beam of typical wavelengths to achieve the high-power and high-energy laser output. Through the simulation analysis of the thermal effect of dichroic mirrors and the far-field laser parameters of beam combination spot, the simulation results of the thermal effect showed that the root-mean-square value of surface thermal deformation of dichroic mirror was 0.004 λ (λ=632.8 nm) with the single laser beam power of 10 kW and the light spot diameter of 15 mm, which satisfied the design requirements of optical elements surface accuracy less than 0.03 λ. Finally, an experimental system based on dichroic mirror of spectral beam combination was developed. The beam combination test of high-power continuous laser and high-power continuous laser, high-power continuous laser and high-energy pulsed laser were carried out respectively, and the beam combination efficiency was higher than 95%. The experimental results show that the spectral beam combination can be effectively applied to the field of high-energy laser.