The invention discloses a calibration method of parasitic capacitance of a charge type SAR-ADC. The charge type SAR-ADC comprises an LSB capacitor array, all upper polar plates of the LSB capacitor array are connected with one end of a first compensation circuit, the other end of the first compensation circuit is connected with an arbitrary constant potential, the first compensation circuit is composed of a first fixed capacitor Cd1 and a first adjustable capacitor Cd1', which are connected with each other in parallel, and the nonlinear error of the SAR-ADC is adjusted by adjusting the first compensation circuit. A unit capacitance value in the LSB capacitor array is Cu, the LSB capacitor array has L orders in total, the capacitance values progressively increase from the low order to the high order in a twice relationship, and the capacitance value of the highest order is 2L-1Cu. When the total capacitance value of the LSB capacitor array is CLt, the following relational expression isset up: CLt=(2L-1).Cu+Cdl+Cdl'. By adoption of the calibration method of the parasitic capacitance of the charge type SAR-ADC, very high linearity and gain adjustment precision can be achieved, and the calibration method is particularly suitable for the design of high-precision ADCs.