The invention relates to the field of component detection, in particular to a digital signal processing and controlling system of a non-dispersive infrared gas analyzer. A digital signal processor (DSP) is used as a core of the digital signal processing and controlling system. The digital signal processing and controlling system comprises a DSP chip, an infrared signal conditioning circuit, a 24-bit analog-to-digital converter (ADC) circuit, a temperature acquiring circuit, a gas pressure acquiring circuit, a 16-bit ADC circuit, an external expansion static random access memory (SRAM) circuit, a ferroelectric memory circuit, a real-time clock circuit, a reset circuit with a watchdog and a power monitor, a thermal resistance driving circuit, a key circuit, a digital output circuit, an RS-232/485 interface, a liquid crystal display circuit, a 4-20mA/0-20mA output circuit and software. The amplitude of signals is solved by a spectral analysis method based on fast Fourier transform (FFT), the center of gravity is corrected, the amplitude of the signals is measured accurately, and signal processing accuracy is guaranteed; a mathematical model which meets requirements on engineering application is set up, and the relation between input and output is non-linearly corrected; and temperatures are controlled by using a proportion-integration (PI) control algorithm based on pulse-width modulation (PWM).