An electronic cigarette chip with automatic closed-loop control for output voltage, wherein the electronic cigarette chip comprises a built-in microcontroller calculation MCU module, a full bridge buck-boost module, an output voltage feedback circuit module, an internal power module, an operational amplifying unit module, and a plurality of signal terminals, the full bridge buck-boost module comprises four N-channel MOS transistors and four PWM driving logic circuits, the built-in microcontroller calculation MCU module is connected with and configured to control the four PWM driving logic circuits respectively, the four PWM driving logic circuits are respectively connected with and configured to control the four N-channel MOS transistors, the four PWM driving logic circuits comprise a first PWM driving logic circuit, a second PWM driving logic circuit, a third PWM driving logic circuit, and a fourth PWM driving logic circuit, the four N-channel MOS transistors comprise a first N-channel MOS transistor, a second N-channel MOS transistor, a third N-channel MOS transistor, and a fourth N-channel MOS transistor, the first PWM driving logic circuit is further connected with a signal terminal BOOT1 and a signal terminal SW1, the fourth PWM driving logic circuit is further connected with a signal terminal BOOT2 and a signal terminal SW2, the first N-channel MOS transistor is electrically connected with the second N-channel MOS transistor, the fourth N-channel MOS transistor is electrically connected with the third N-channel MOS transistor, the first N-channel MOS transistor is further connected with an external input voltage signal terminal VIN, the fourth N-channel MOS transistor is further connected with a signal terminal VOUT, the signal terminal VOUT serves to provide output voltage to a heating element of the electronic cigarette, the second PWM driving logic circuit, the second N-channel MOS transistor, the third N-channel MOS transistor and the third PWM driving logic circuit are respectively arranged with a port connected with a grounding terminal PGND, the output voltage feedback circuit module is configured to feed output voltage of the signal terminal VOUT back to the built-in microcontroller calculation MCU module, the internal power module is configured to step up input voltage of the signal terminal VIN and then supply power to the four PWM driving logic circuits, a signal terminal IN+ and a signal terminal IN- are connected with the operational amplifying unit module, the signal terminal IN+ is configured to be connected with the signal terminal VOUT, the signal terminal IN- is configured to be connected with an end of the heating element, the signal terminal IN+ and the signal terminal IN- are configured to be connected with a resistor, the operational amplifying unit module is configured to generate a differential analog signal by amplification operation and send the differential analog signal to the built-in microcontroller calculation MCU module, the built-in microcontroller calculation MCU module is configured to generate a resistance signal by operations and send the resistance signal to an external chip, and the built-in microcontroller calculation MCU module is configured to perform operations with a high degree of accuracy based on a setting signal of the external chip and a feedback signal of the output voltage feedback circuit module, and automatically control the full bridge buck-boost module, to provide precisely adjustable output voltage by the signal terminal VOUT.