A windmill is a device used for Wind Energi Conversion Systems. The function of this windmill can convert the kinetic energy of wind into mechanical energy in the form of a round rotor. The object of this research is comparison of the number of blades at the savonius windmill. Performance testing use natural wind. Testing in the research using natural wind. The wind speed used is 3.4 m/s , 4.7 m/s , 5.8 m/s with variations in the number of blades 3, a number of blades 4 and the number of blades 6. The result showed that the savonius windmill with variations in the number of blades 3, a number of blades 4 and the number of blades 6 have different result. In this research the highest round rotor produces 80.1 rpm with wind speed 5.8 m/s at blades 3 while the lowest round rotor produces 45.8 rpm with wind speed 3.4 m/s at blades 3. Minimum tip speed ratio on variations in number of blade 6 with wind speeds of 5.8 m/s=60.33 while maximum tip speed ratio on variations in number of blade 4 with wind speeds of 3.4 m/s=85.05 .