The application discloses a defoaming device of falling film evaporator, which comprises a shell, the shell is provided with a steam inlet at the bottom and a steam outlet at the top, at least one vertical defoaming channel and a steam guiding mechanism are arranged in the shell, the defoaming channel is provided with an input port connected with the steam inlet and an output port connected with the steam outlet, the steam guiding mechanism is used for guiding steam to flow into the input port of the defoaming channel, and the width of the defoaming channel gradually decreases along the guiding direction of the steam guiding mechanism. The application has the beneficial effects of improving the defoaming effect and efficiency.