||The loop gain of a dc-dc switch mode power converter (switching converter) is crucial in determining the system stability and response. Researchers have been employing open loop technique in measuring the control to output transfer function Vo(s)/d(s). For closed loop measurements, only the small signal line regulation Vo(s)/Vg(s) has been obtained, and we learn no direct measurement of loop gains being mentioned previously. Discrepancies in the modelling of loop gains are fully recognized in the power electronics community, and comparison of different modelling techniques through correct loop gain measurement is thus imperative. This is especially true in modelling DCM (discontinuous conduction mode) converters. Hence, the purpose of this research is threefold. (1) Theoretical aspects of loop gain measurement are studied, and practical loop gain measurement of several converter configurations are presented. (2) A new simulation method on the Matlab platform is presented in computing the loop gains of switching converters. This method allows an exact simulation that accounts for parasitics of converters. Buck, boost and flyback converters operating in the continuous conduction mode (CCM) and the DCM are performed and compared among existing models. (3) Finally, the salient features in modelling of DCM converters are discussed, and theoretical results are compared with the new simulation result.