In order to achieve optimization of the structure of pleated filter bag, the three-dimensional geometric models of pleated filter bag were correspondingly established under different pleat numbers based on ɑ, which was the ratio of pleat height to pleat width. Then the gas flow field characteristics of pleated filter bags were simulated with porous medium and standard k?? model under some circumstances that when the pleat number N=8, 12, 16, 20, 24 and bag length L=2.5, 3.0, 3.5 m. The results showed that under the same inlet velocity, the filtration resistance of pleated filter bag with the number of pleats N=12 (ɑ=1.12) was smallest, and the growth rate of the filtration resistance was significantly no larger than the other four number of pleats, the distribution of the flow field inside the bag house was more uniform, so the pleated filter bag with N=12 was better adaptable to different treatment air volumes. The filtration resistance of pleated baghouse precipitator with different bag lengths increased with the increase of inlet velocity in the form of a quadratic curve. When the air volume was small, the longer the pleated filter bag was, the smaller the pressure drop of system was, but the pleated filter bag was too short or too long to fit the operation condition of high air volume due to the large pressure drop of the system. The pressure gradient in vertical of the filter bag with L=3.0 m was relative less, both the pressure and velocity distribution in the bag house were relatively more homogeneous, which was beneficial to protect the filter bag and energy-saving.