Description of the developed mobile controlled source radiomagnetotelluric sounding system (CSRMT) with ungrounded towed transmitting and receiving electric lines is presented. The measuring unit contains electric line, three magnetic sensors and inertial navigation system for measuring the orientation of magnetic sensors. Comparison of apparent resistivity values obtained from measurements of signals from the controlled source and remote radio transmitters shows good agreement. During the work, signals from the controlled source are recorded at the main frequency of 60 kHz and its subharmonics. To ensure a depth of study of the section up to 40 m, together with measurements of the field of the controlled source, signals from remote VLF radio transmitter are used at lower frequencies. Survey is performed at a speed of 15–20 km/h. Based on the measurements along the Nadym – Salekhard road, a resistivity section was obtained, confirmed by drilling. Thawed zones are distinguished by lower electrical resistivity values. Moreover, the resistivity section is significantly more detailed than the borehole section. The prospects for using the developed mobile CSRMT system in the study of permafrost are considered.