The invention discloses a variable mass system of vertical air shaft explosion door and a control method thereof; the variable mass system of vertical air shaft explosion door comprises a main water tank, a water pump and variable mass water tanks which are connected by pipelines; a water knockout trap is arranged inside the pipeline between the main water tank and the variable mass water tanks; the water knockout trap is respectively connected with a plurality of variable mass water tanks by pipelines; the pipelines between the water knockout trap and the main water tank form a pipe range for supplying and discharging water of the variable mass water tanks; the water pump is installed in the pipe range. The variable mass system of vertical air shaft explosion door can not only achieve fast supplying and discharging water of the vertical air shaft explosion door variable mass system, but also can achieve slow supplying and discharging water of the vertical air shaft explosion door variable mass system, can further precisely control the mass variations of mass portions, thereby ensuring stably resetting or lifting the vertical air shaft explosion door, saving time, and being safe in operation.