In total light scattering particle sizing technique, the calculation of extinction efficiency based on Mie theory can only be applied to the homogeneous spherical particles, what is important is that the Mie theory is expensive in both time and resources. Using the anomalous diffraction approximation (ADA) instead of Mie extinction efficiency can simplify the inversion of particle size distribution. The feasibility and limitations of using the anomalous diffraction approximation for calculating the extinction efficiency of circular cylinder particles are investigated. The genetic algorithm is used to inverse the particle size distribution under the dependent model algorithm. Simulation experiments illustrate that it is feasible to use the anomalous diffraction approximation to inverse the circular cylinder particle size distribution in the total light scattering technique, and the inversion results are steady and reliable. The inversion error is 5.7% when 3% relative error is put in the extinction measurement values. The method has advantages of simplicity, rapidity, and suitability for in-line particle size measurement.