The invention discloses a forecasting method of a solar activity longitude zone. The method mainly comprises the following steps: selecting solar X-ray flare data (sunspot data are used in the case of no solar flare in a solar activity minimum period); determining relevant solar rotation parameters and a present position of the solar activity longitude zone (Carrington coordinate) according to the selected observation data; forecasting a central position (the Carrington coordinate) of the solar activity longitude zone within a certain period according to the determined solar rotation parameters and the present position of the solar activity longitude zone; and converting the Carrington coordinate of the forecast central position of the solar activity longitude zone into a heliographic coordinate to forecast a heliographic position of the solar activity longitude zone. The forecasting method enriches the long-term solar activity forecasting contents and provides a certain reference value for the short-term solar activity forecasting. In addition, the method has strong operability, which reduces the subjectivity of a forecaster.