The invention discloses a gas differential absorption laser radar based on a non-coherent light source. The laser radar uses a non-coherent light source, laser of two operating wavelengths is filtered by a filtering technology, one operating wavelength is positioned on the peak value of a gas absorption line, the other operating wavelength deviates from the gas adsorption line, and the differential adsorption detection of an atmosphere gas ingredient can be realized through the detection of the atmosphere echo signal of two beams of laser. A time division multiplexing technology is adopted, only one detector is used for finishing the measurement of reference laser and signal light, and a system integration level is improved. According to the gas differential absorption laser radar, the gas (such as water vapour, CO2, HCN, CO and the like), which is positioned in a non-coherent light source frequency spectrum range, of the gas adsorption line can be realized. A non-coherent detection technology, a wavelength division multiplexing technology and the time division multiplexing technology are adopted to realize the detection of gas ingredients, and the gas differential absorption laser radar has the advantages of high system integration degree, all fiber linking, compact structure, low construction cost, relatively safe human eyes and the like.