Abstract: Uncertainty forecasting of renewable energy power is of great significance to improve the capacity of renewable energy consumption and ensure the power systems' safe and stable operation. Uncertainty forecasting, which includes interval forecasting, probability forecasting, and scenario generation, is a hot research topic. Compared with deterministic forecasting, uncertain forecasting can provide richer information and reflect the uncertainty of renewable energy power from more dimensions such as the change interval, the probability of occurrence, and the possible scenarios. Based on the clues of interval forecasting, probability forecasting, and scenario generation, this paper summarizes the uncertainty forecasting techniques of renewable energy power. The development trend of uncertainty forecasting of renewable energy power is analyzed from the number of published papers, year, distribution of journals, and other aspects. The classification of uncertainty forecasting technology is introduced. The theory and model of uncertainty forecasting are described, and the existing renewable energy power forecasting system and uncertainty forecasting evaluation indexes are summarized and analyzed. Finally, combined with the research status and development trend of renewable energy power forecasting, the research direction worthy of attention is put forward. The research results of this paper provide references for the research on uncertainty forecasting of renewable energy power.