Abstract: OBJECTIVE To explore the air environment control in ship negative pressure ward and conduct the risk assessment. METHODS STARCCM+ simulation software was employed to simulate the air environment in the negative pressure ward of ships, and the impact of ventilation volume, non-equilibrium pressure difference and open/close door disturbance on the flow of polluted gas in the ward and the pressure control between compartments was observed. RESULTS It was found that the pressure gradient and airflow direction of adjacent cabins were basically the same under different ventilation conditions; the pressure fluctuation of the medical corridor had the greatest impact on the buffer room, and when the negative pressure fluctuated higher than the design value, the pressure difference between the buffer room and the negative pressure ward was lower than the design requirement of 5 Pa; when the cabin door was opened from the buffer room to the corridor, that was, when the cabin door was opened to an area with low negative pressure, a low pressure area appears in the buffer room, and the polluted air flowed from the corridor to the buffer room. Finally, the risk of airborne infection was assessed by using the Wells-Riley model, doubling the amount of ventilation reduced the probability of transmission of SARS-CoV-2 infection by about 100%. The results showed that the ventilation volume had little effect on the pressure control, but it wound affect the probability of transmission of viral infection; the pressure fluctuation in a certain compartment would affect the pressure in other areas, so that the pressure control between the compartments did not meet the design requirements, opening the hatch door to the area with low negative pressure could reduce the risk of virus transmission. CONCLUSION The research provides guidance for the air environment control in the ship's negative pressure isolation ward so as to prevent the spread of infectious diseases in the ship.