The invention provides a centralized frequency conversion smoke discharging control method and device applied to a centralized smoke discharging system. The centralized smoke discharging system comprises a public flue. Each kitchen in each floor is provided with a check valve, a connecting pipe and a kitchen ventilator, all of which are connected with the public flue. Firstly, the floor where thekitchen ventilators are started is obtained, and the outlet air volume and the outlet air pressure of the public flue are obtained according to the number of the started kitchen ventilators and the rated air volume of each started kitchen ventilator; according to the outlet air volume, the outlet air pressure and the resistance coefficient, the work air pressure of the started kitchen ventilatorsis sequentially calculated according to the sequence from top to bottom; according to the work air pressure of each started kitchen ventilator, the target running frequency of the started kitchen ventilator is calculated; and the target running frequency of each started kitchen ventilator is sent to the corresponding started kitchen ventilator, and accordingly the corresponding started kitchen ventilator works according to the target running frequency. According to the centralized frequency conversion smoke discharging control method and device, the smoke discharging flow can be controlled inan oriented manner, balanced distribution is achieved, accordingly, the smoke discharging pressure of the kitchens is relieved, the integral smoke discharging efficiency of the floor building is improved, the kitchen ventilators in all floors are controlled to conduct frequency conversion running in order, and high efficiency and energy saving are achieved.