Using the laser scattering wetness sensor, the data processing method of turbine last stage wetness measuring in the thermal power station has been researched. Firstly, we calculate the results of the vapor phase function using Mie scattering theory, and get the most probable radius of liquid water droplets at the end-turbine by the method of the look-up table and inversion fitting; Then according to the generalized Gamma distribution of the steam condensation water under the particle size, using the most probable radius of liquid water droplets we get before and using some related spectrum parameters to calculate the of liquid water content at the end-turbine; then using the pressure and temperature in the steam turbine and according to the ideal gas equation to calculate the dry steam content, the temperature and pressure is measured by temperature sensor and pressure sensor in the turbine; At the end, use the liquid water content, dry steam content and the definition of dryness fraction to calculate the dryness fraction at end-turbine.