In the total light scattering particle sizing technique,a method based on the improved genetic algorithm is proposed to be applied to the inversion of particle size distribution. In the independent model, the improved genetic algorithm combined with simulated annealing algorithm overcomes the difficulties of determining the penalty coefficient of genetic algorithm based on the penalty function, which will cause the inversion result to be an infeasible solution. In the dependent model, the size distribution is well determined at only three wavelengths by the improved genetic algorithm. It is feasible to use the improved genetic algorithm to recover the particle size distribution in the total light scattering technique and the inversion results are steady and reliable, which avoids the defects that the simple genetic algorithm is easy premature and then the inversion result is easily trapped in a local solution.