The invention relates to the field of car dumpers and discloses a materialplanner cleaning device of a car dumper, a car dumper system and an unloading method of the car dumper system. The materialplanner cleaning device comprises a cleaning module (1) for cleaning a materialplanner, a control module for controlling the cleaning module (1), and a measuring module electrically connected with the control module and used for measuring the overturning angle of a carriage dumping materials into a hopper of the car dumper. The control module is arranged to control the cleaning module (1) to clean the materialplanner after receiving the information, fed back by the measuring module, of overturning of the carriage from the horizontal position to a first preset angle, and thus the cleaning module can clean the materialplanner within the time quantum when the carriage is overturned to enable a material flow to shield a detection route of a measuring device or to enable material flying dust to affect the measuring result of the measuring device. The car dumper operates circularly, the cleaning device can conduct cleaning operation circularly correspondingly, measurement of the materialplannercannot be affected, and meanwhile the accuracy and stability of the measuring result of the materialplanner are ensured.