A phytoplankton bright-field fluorescence microscopic simultaneous imaging system was designed to solve the problems of the conventional phytoplankton species identification microscopy method， such as the difficulty of distinguishing between similar morphological algal cells， interference of impurities of the same particle size， and difficulty in locating and segmenting the algal cells. The proposed system uses a high-resolution microscopic imaging optical path structure， combined transmission-fall illumination method， and simultaneous bright-field fluorescence dual-optical imaging method with a spectral optical path to capture bright-field morphological and fluorescence images of phytoplankton with pigment information. The system was tested for the simultaneous acquisition of bright-field and fluorescence images of different algal species， including chlorophyta， cyanophyta， and bacillariophyta. The experimental results indicated that the imaging resolution of the system was 1.5 μm， imaging period was 707 ms， texture of algal cells in the images captured by the system was clear， and cell edges were obvious. The system using the method of combining the bright-field images with fluorescent images can effectively locate the algal cells， reduce the influence of impurities in the samples on the procedure of algae identification， and increase the amount of information obtained from the algal microscopic images. This study provides a methodological reference for related research based on phytoplankton microscopic images.