The transport of runaway electrons in a high-temperature plasma is relatively easy to measure in a steady state experiment and a perturbation experiment, which provides runaway electron diffusion coefficient Dr. This diffusion coefficient is determined by inteal magnetic fluctuations, so it can be interpreted in terms of a magnetic fluctuation level. The inteal magnetic fluctuation level (br/BT) is estimated to be about (2-4)×-4 in the HL-1M plasma. The results presented here demonstrate the effectiveness of using runaway electron transport techniques to determine inteal magnetic fluctuations. A profile of magnetic fluctuation level in the HL-1M plasma can be estimated from Dr.