Experimental and numerical investigations to study the effect of adding one slot to the impeller blades on the rotating stall and pressure fluctuations in a high-speed centrifugal blower. The experimental test rig includes a blower of the centrifugal, transducer of pressure as well measurement instrumentations which were constructed for this study. A data acquisition system (hardware) and its (software) have been developed to transfer the signal from the transducer of pressure to the computer then analysis with time. The experimental work has been implemented by measuring the static pressure variation as well fluctuating of pressure for two cases of impeller (without slot and with one slot). Static pressure has been taken in different points prepared on the front wall of the volute casing along one track for two cases of the impeller. This track is an angular track about the impeller. The results of the experiment show that the fluctuations of pressure increase with the mass flow rate decrease. Also, the results indicate that fluctuations of pressure decrease with adding slots into the impeller blades. The simulation of numerical has been carried out on blower of centrifugal into analysis both field of flow and fluctuations of pressure through using ANSYS (FLUENT 15). The simulation of numerical has been completed through solve the continuity and momentum equations with the moving reference framework technique inside the blower. The numerical simulation results show a good agreement with the results of the experiments.