The invention discloses a shielding effectiveness measuring method, measuring system and calibration system of a shielding material and relates to the technical field of shielding effectiveness measuring methods. The shielding effectiveness measuring method includes following steps that the shielding material which is measured divides a reverberation chamber into an electromagnetic transmitting area and an electromagnetic receiving area; a signal source is arranged outside the reverberation chamber and connected with a transmitting antenna of the electromagnetic transmitting area to transmit signals in a form of electromagnetic waves; electromagnetic reference power of the signal source is measured in the electromagnetic receiving area before the shielding material is mounted; electromagnetic measuring power of the signal source is measured in the electromagnetic receiving area after the shielding material is mounted; shielding effectiveness of the shielding material is measured according to the reference power and the measuring power. By the measuring method, shielding effectiveness of the shielding material in each incident direction can be measured, and testing of the shielding effectiveness is more accurate.