A hydrogen beam probing system developed for the REPUTE‐1 reversed field pinch device is described. With this system, the plasma ion line density, the central ion temperature, and the magnetic field profile can be measured. Before being applied to the REPUTE‐1 device, the probing system was tested on the TORIUT‐5 tokamak and TORIUT‐6 ultralow‐q (ULQ) devices. The experimental results show the availability of the system. The measured line density agrees well with that measured by the microwave interferometry. The measurable density ranges from 1019m−3to 3×1020m−3. A new method of magnetic field measurement which is effective and important for RFP plasmas is proposed. The resolution and the accuracy of this measurement have been confirmed by experiments on the TORIUT‐5 device. Experimental results agree well with computation.