The invention relates to the technical field of power quality analysis, and particularly relates to a capacitor capacitance value and change trend forecasting method based on a time series method. For the lack of effective capacitor capacitance value and change trend forecasting in the prior art, the invention provides the capacitor capacitance value and change trend forecasting method based on the time series method. According to the invention, sample data are collected; a capacitance value change trend forecasting model is established; a capacitance value forecasting model is established; a capacitance value is forecasted; and effective and accurate capacitor capacitance value and change trend forecasting is realized. The algorithm provided by the invention has the advantages of comprehensive design consideration, low implementation cost, reliable forecasting effect and broad application prospect, and is compatible with various types of capacitors of the existing power industry.