Clock Scanning Microwave Interferometric Radiometer (CS-MIR) is a new concept of synthetic aperture radiometer. It has the advantages of simple array structure, easy deployment and resultingly being able to achieve high spatial resolution. Recently a ground-based prototype of CS-MIR working at L-band has been developed. This paper presents the calibration method of this instrument. Compared with the SMOS/MIRAS system, the calibration of the CS-MIR is much simple. The simplicity is mainly lies in three aspects: It does not need quadrature error correction because of the digital I/Q demodulation, not need PMS subsystem for visibility demoralization and not need correlated noise injection for phase calibration. © 2018 IEEE.