Abstract: In order to adapt to the rapid detection of particle size of fly ash in industrial field, the fly ash particle size distribution reconstruction by fruit flies optimization algorithm was studied. An online measurement platform for particle size is set up. The standard fly ash particles were used as experimental materials to simulate the experiment under noisy environment. The particle size of the fly ash particle was calculated by fruit flies algorithm and the results were compared with those obtained by genetic algorithm and particle swarm algorithm. The results show that the particle size of the particle is 1.07% and the calculation time is 1.21 s by fruit flies optimization algorithm. Compared with the other two algorithms, it has good inversion accuracy and fast iteration speed.