Öz In this study, harmonics analyzer circuit based on PIC 18F4620 microcontroller has been designed. After implementation of simulation of the circuit on Proteus program, the circuit has been printed on card. In the implemented circuit, data has been processed using PIC 18F4620 microcontroller and at the same time by using microcontroller through RS-232 data bus the data has been transferred to Matlab. By analyzing data sent to matlab, the circuit has been verified. By taking Fast Fourier Transform (FFT) of sample signal applied to analog-digital converter input of PIC 18F4620 and using programs placed inside microcontroller, the implemented system helps to analyze the frequency spectrum. Due to the availability and low price of the material used, the applicability of the circuit has increased. Beside its low budget, the used circuit has shown good performance