Abstract: In order to study the effect of wet steam characteristics on the normal operation of the steam turbine unit,a new method was proposed to measure the diameter of the wet steam based on laser scattering principle and co-CCD imaging principle.After simulation,the effect of the size parameter,acceptance angle and other parameters on the backscatter intensity was obtained,optimal parameters were known.When the acceptance angle is 180°and receiver distance is 0.5m,a higher proportion of the scattering can be obtained.The results can provide a good reference for actual measurements.