Experimental and numerical investigations to study the effect of adding slots to the blades on the rotating stall phenomenon and pressure fluctuations in centrifugal blower. The experimental test rig which concludes a centrifugal blower, pressure sensors and measurement instrumentations are design and constructed for the present work. The experimental study has been carried out by measuring the static pressure variation and pressure fluctuation for two cases of impeller (with and without slots). Measuring of static values has been completed at various points prepared on the front-wall of the volute casing along one path for two cases of impeller. Enhancement in pressure distribution adds slots to the blades comparison with cases without slots at values of mass flow rate between non-flow and 0.02254 kg/s. The pressure fluctuations increase with decrease values of mass flow rates. We concluded also that pressure fluctuations decrease with adding slots to blades. This led to decrease occur of rotating stall phenomenon and increase stability of centrifugal blower. Numerical simulation has been carried out on present centrifugal blower to analyze both flow field and pressure fluctuations by using FLUENT 14 package. The numerical simulation has been completed by solving the continuity and momentum equations with moving reference frame technique inside the blower. The results of numerical simulation give a good agreement with the experimental results.