Taking the Platymonas subcordiformis as sample and the Nd∶YAP laser (1 341 nm)as the light source, the effects on chloroplast autofluorescence intensity and chloroplast area of Platymonas subcordiformis irradiated by laser were studied using confocal laser scanning microscopy. The autofluorescence images and fluorescence spectra of the Platymonas subcordiformis irradiated by Nd∶YAP laser were obtained by the excitation of 488 nm Ar+ laser. The results showed that all the laser irradiation dose, except the irradiation group with parameters of 10 W power and 60 s duration time, improved the autofluorescence intensity of Platymonas subcordiformis, and all the doses increased the chloroplast area. The laser can stimulate the chloroplast evelopment of Platymonas subcordiformis, promoted the growth of algal cells and improve the activity of chloroplast photosynthesis.