The invention relates to an automatic tank sealing machine, in particular to a desktop type automatic tank sealing machine. The desktop type automatic tank sealing machine comprises a bottom frame, wherein a machine frame is fixed at the upper end of the bottom frame, a machine shell seat is installed at the upper end of the machine frame, a bottom shell is arranged in the machine shell seat, a bottom support is arranged at the upper end of the bottom frame, the bottom support is limited and fixed through a plunger hole in a bottom supporting column, and a screw rod is installed at the lower end of the bottom support; a motor is arranged at the top of the machine shell seat, the motor is in transmission connection with a power input shaft in a belt cover through a small belt wheel and a belt, the belt cover is arranged on the machine shell seat, a large belt wheel is installed on the belt cover in cooperation with the small belt wheel, a starting transverse pressing rod, a pulling positioning pin and a clutch are connected inside the large belt wheel, and a torsion spring and a shifting fork are connected to the starting transverse pressing rod; and a cam is arranged in the bottomshell, a pressure head is installed on the bottom shell, and the pressure head is connected to the large belt wheel. The desktop type automatic tank sealing machine is compact and exquisite, low in motion noise, small in size, capable of being placed in a laboratory table top to be sealed, high in applicability, high in tank sealing speed, good in effect and simple to operate.