AC induction motors are widely used in industrial applications. These motors are generally worked in variable speed. Speed control of the AC motors are more complex compared with the DC motors. In this study, a three phase induction motor speed controller is designed and imlemented by using 8-bit microcontroller. Six step inverter is controlled by microcontroller which produce PWM signals by using lookup table and variable speed has been obtained by changing the voltage and its frequency at the output of inverter. Designed system which uses 8 bit microcontroller is low cost and can be implemented easily.