Abstract: In view of the background of the current global pandemic of respiratory infectious diseases, indoor airborne transmission routes has attracted widespread attention, especially the investigation of the transmission mechanism of respiratory infectious diseases in densely populated environments, such as offices. Fluent software was used to simulate the multiphase flow to explore the impact of the superposition effect of the human thermal plume on aerosol transmission in office environments with different personnel densities. By integrating the modified Wells-Riley equation, the infection probability of susceptible individuals was estimated. The results indicate that in the scenario with a single person, the aerosol particles released by the infected individual's cough traveled a maximum propagation distance of 0.735 m. However, when three individuals stand side by side, the thermal plume generated by neighboring human bodies results in the reduction of the propagation distance of the particles released by the cough of the infected person in the middle to 0.490 m. Under the condition of constant exposure time, the infection probability for the susceptible indiviuals to the left and right of the infected person is 0.167% and 0.191% respectively; for the susceptible person 1 m in front of the infected person, the infection probability is 0.207%. When a susceptible individual stands between two infected individuals, the infection probability for the person in the middle significantly increases to 0.374%. It is evident that thermal plume superposition affects the aerosol propagation distance, which in turn alters the infection probability. In densely populated environments like offices, it is crucial to focus on scientific planning of spatial layouts and personnel distribution to optimize the indoor ventilation patterns.