Phaeodactylum tricornutum is an excellent microalgae of  the biodiesel production, it is obviously necessary to monitor the photosynthesis and growth parameters of microalgae through the culture process. In this study, the cell density was monitored by cell count, and chlorophyll fluorescence parametes, nitrate content in the culture medium, cell chlorophyll fluorescence intensity and neutral fat relative content were detected by using the MultiColor PAM, NanoDrop UV spectrophotometer and fluorescence spectrophotometer, respectively. The results showed that the number of cells and chlorophyll fluorescence intensity had a linear relationship only at the growth phase, after reaching the stationary phase, the chlorophyll content significantly decreased, when chlorophyll fluorescence intensity was not proportional to cell density. The maximum photochemical quantum efficiency Fv/Fm of PSII which showed two ascending and descending processes in the culture stage was positively correlated with the specific growth rate of chlorophyll fluorescence intensity. The photochemical quenching coefficient qL increased in the culture process, while the relative electron transport rate rETR and the actual photosynthetic efficiency Y (II) both showed the trend of rising first and then down. The content of nitrate in the culture medium decreased to a certain extent, and then no longer reduced. The cell neutral fat relative content decreased after 1 day of cell inoculation and then continued to increase after the nitrate content did not decrease any more. In this study, the correlation data of photosynthesis and growth parameters, and the establishment of the method for measuring nitrate content in the culture medium and cell neutral fat relative content, can provide the necessary detection methods and research foundation for the laboratory culture and metabolite accumulation of P. tricornutum.