Pyrolysis of microalgal biomass is a potential strategy for biofuel production. In this work, the pyrolysis characteristics of microalgae, Tetraselmis sp., were systematically explored under isothermal and nonisothermal conditions. Analysis of nonisothermal decomposition of microalgae under nitrogen atmosphere at different heating rates (5, 10, 15, and 20℃ min-1) revealed that the conversion of microalgae was significantly affected by the heating rate and reached ~90% at approximately 500℃. The mean activation energy for the pyrolysis of Tetraselmis sp. was calculated using model-free Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods. Microalgae pyrolysis in a micro-tubing reactor was performed at various temperatures (360-400℃) and for different reaction times (0.5-3.0min). The results indicated that the maximum yield of biocrude (49.5 wt%) was attained during pyrolysis at 400℃ for 2min. It was established that the chemical composition of the biocrude was significantly influenced by the pyrolysis conditions. A quantitative model was used to evaluate the composition of carbohydrates, proteins, and lipids in the microalgae. This facilitated the determination of individual biochemical components in the pyrolytic products. Furthermore, the time- and temperature-dependent yields of the solid residue, biocrude, and gas were predicted, providing critical information for microalgal pyrolysis design, control, and performance.