In order to enrich the optimization theory of hubless pump-jet thruster noise performance, the influence of blade number on the performance of hubless pump-jet thruster was studied, and the variation law of pressure pulsation in hubless pump-jet thruster with different number of blades was emphatically investigated. Based on the finite volume element method of computational fluid dynamics, the RANS equation was discretized, and the calculation model was closed by using RNG k-ε turbulence model, coupling the pressure-velocity by using the SIMPLEC. The unsteady numerical simulation of the flow field inside the hubless pump-jet thruster with different number of blades was carried out, and the calculated results were compared and analyzed in detail. The study results show that with the increase of blade number, the head, efficiency and thrust of hubless pump-jet thruster model increase gradually. The pressure distribution on the blade surface becomes more uniform. The pressure pulsations of the impeller rim and the middle part decreased obviously. The amplitude of pressure pulsations at the main frequencies of impeller inlet and outlet decreases gradually from rim to center.