A monitoring system and a monitoring method for a planter includes a computer having an unit speed fusion module, a seeding flow rate monitoring module, and a decision module for theoretical rotation speed of a drive motor, a rotation speed deviation inference module, a controlling parameter tuning module, an adjusting module for rotation speed of a seeding shaft, a controlling module for rotation speed of seeding shaft and a positioning signal receiver fixed on a top of a cab for receiving a geographic position signal. The system monitors operating state parameters of the planter and accurately controls seed amount.