In this paper, the assessment of SAR probe and the prediction of SAR system measurement are presented. Usually, SAR probe have got high output impedance. Then, the response time is directly affected by the acquisition system (input impedance, cable length). Firstly a methodology is presented to define a circuit model of the SAR probe by comparison measurement and simulation. Then, it is possible to predict the time response of a SAR system including cable, matching circuit and data acquisition.