The space mission MICROSCOPE aims at testing the Equivalence Principle (EP) with an accuracy of 10-15. The test is based on the precise measurement delivered by a differential electrostatic accelerometer onboard a drag-free microsatellite which includes two cylindrical test masses submitted to the same gravitational field and made of different materials. The accuracy of the measurement exploited for the EP test is limited by our knowledge of the physical parameters of the instrument. The on-ground evaluation of these parameters is not precise enough. An in-orbit calibration is therefore needed to finely characterize these instrumental parameters in order to correct the measurements. The calibration procedures have been determined and their analytical performances have been evaluated. In addition, a software simulator including models of the instrument and the satellite drag-free system has been developed. After an overall presentation of the MICROSCOPE mission, this paper will focus on the description of the simulator used to validate the specific procedures which are planned to determine in-orbit the exact values of the driving parameters of the instrument.