A main rotor blade calibration gauge is disclosed to include a graduation plate with an angle scale, a calibration plate pivoted to one end of the graduation plate, and chuck plates coupled to the calibration plate for securing the calibration plate to the main rotor blade of the remote-controlled toy helicopter to be adjusted for allowing the angle of the main rotor blade to be calibrated subject to the indication of a pointer at the calibration plate relative to the angle scale at the graduation plate.