The occurrence of harmful algae on the coast of Korea has been a cause of damage to the aquaculture industry and deterioration ofthe coastal ecosystem environment. A method is required to predict their outbreak in real-time at the site. Therefore, this study attemptedto develop a small hybrid optical sensor and real-time monitoring system based on LiDAR that can be used in the field and laboratoryand can be applied to various platforms. FMS-L specifically suggested the amount of Chlorophyll a (Chl a) in the sample by measuring andanalyzing the fluorescence emitted by the irradiating light. The accuracy of FMS-L was verified by measuring the concentrations of standardChlorophyll a substances and Margalfidinium polykirkoids. In addition, the precision was verified by comparing the measurement results ofFMS-L using commercial equipment Phyto-PAM-II. This equipment is compact and easy to move. Therefore, it can be easily applied to fieldsurveys, allows short time measurements (10 s), and can be applied at a distance of 10 m from the measurement site.