Online junction temperature (Tj) measurement is critical for SiC MOSFET reliability evaluation health management and life prediction. In order to make the tradeoff between availability, simplicity, as well as accuracy, this article demonstrates a real-time junction temperature estimating method by selecting the current oscillation peak of drain source (Ioscpeak) during turn-on transient as a temperature sensitive electrical parameter (TSEP). The theoretical and simulation analysis results show that the Ioscpeak is available to be a TSEP. Then, the model of Ioscpeak and Tj is derived through fitting curve based the experimental results. The voltage and load current dependency of proposed method are also discussed. The experimental results demonstrate that the bus voltage level has a negligible influence to the relationship between the Ioscpeak and the Tj, the value of Ioscpeak is increasing with the increment of current level at the specific temperature. The sensitivity of proposed method has a satisfactory performance of junction temperature estimation. The estimation circuit of proposed method has a simplicity hardware with low cost and easy to be implanted with gate drive of SiC MOSFET.