This paper presents a single switch topology of DC-DC multilevel buck-boost converter with very high voltage gain ratio. It is a pulse width modulation (PWM) based multilevel buck-boost converter (MLBBC) consisting of 2N-1 Diodes, 2N-1 capacitors for N level boost converter. The proposed converter topology is a combination of buck-boost converter and cockcroft-walton voltage multiplier. The main advantage of proposed topology is output voltage can be increased by increasing number of capacitors and diodes at output side without disturbing the main circuit. The mathematical analysis and circuit operation discussed. © 2014 IEEE.