The rapid and in situ measuring methods of algae photosynthesis activity by using highlight LED as the excitation light source was presented. Based on the analysis of the absorption spectrum of different algae, the fluorescence induced curve was obtained by using three kinds of excitation light source of measurement light, saturation pulse light and actinic light in the measurement of algae photosynthesis activity. To improve the stability of the excitation light source, the constant current drive circuit based boost circuit was designed to eliminate the effects of the supply voltage fluctuations and temperature changes on the instability of the illumination of excitation light source, and to provide basic parameters for the design of the measurement system of algae photosynthesis activity.