An adjusting device of a light source in position measurement equipment comprises the light source, a main grating which is placed perpendicular to the direction of light rays sent by the light source and is capable of moving relative to the light source up and down, and a photoelectric detector receiving light modulated through the main grating, wherein both the photoelectric detector and a compassion module are connected with an analysis-process module, both the light source and the compassion module are connected with an audion, and light of the light source is modulated through the main grating, enters the photoelectric detector, and is converted to light currents to be inputted to the analysis-process module. Several maximal light current values are sorted out through the adoption of a software algorithm, and an average value is calculated to serve as an actual value. When a system starts to work normally, an average value of several currents in the photoelectric detector is measured to serve as a fixed value, the actual value and the fixed value are inputted to the compassion module to be compared, a modulating difference is calculated and exerted on a base electrode of the audion in a voltage mode, the actual value changes, and currents of the light source are adjusted until the actual value is equal to the fixed value. The adjusting device of the light source in the position measurement equipment is accurate and reliable in measuring results, and strong in anti-pollution capacity.