The measuring cylinders of the filling machine are respectively connected to the filling head, and through the reciprocating motion of the main cylinder, a certain amount of liquid is sucked in, and then injected into the container to be filled. During this process, it is necessary to switch a through valve in a timely manner to change the flow direction of the liquid when the main oil cylinder is reversing. Moreover, during the injection process, in order to accelerate the filling speed without causing liquid overflow, when filling to 90% of the full bottle, a throttle valve connected in series in the injection channel should be opened to significantly reduce the injection flow rate.