The invention provides a tank fermentation method of Pixian thick broad-bean paste. The tank fermentation method of the Pixian thick broad-bean paste comprises the following steps: A, preparing broad bean paste flaps, namely washing broad bean flaps, carrying out steaming, cooling and spread air-dying, inoculating the air-dried broad bean flaps with aspergillus oryzae powder so as to obtain broad-bean-flap zymogenic materials, sending the broad-bean-flap zymogenic materials into a fermentation tank, adding lactic acid bacterium powder and yeast powder, and carrying out fermentation so as to obtain the broad bean paste flaps; B, preparing a chili pepper base, namely crushing chili peppers, putting the crushed chili peppers into a chili pepper base fermentation tank, adding lactic acid bacterium powder, and carrying out fermentation so as to obtain the chili pepper base; and C, adding the broad bean paste flaps into the chili pepper base fermentation tank according to a mass ratio of 4:6, carrying out uniform mixing, adding yeast powder, carrying out uniform mixing, and carrying out fermentation for 45-75 days so as to obtain the Pixian thick broad-bean paste. The tank fermentation method of the Pixian thick broad-bean paste improves aroma and delicious taste of the Pixian thick broad-bean paste, shortens production cycle of the Pixian thick broad-bean paste, and avoids contamination of pathogenic bacteria during production processes under the premise of meeting quality requirements; moreover, the tank fermentation method of the Pixian thick broad-bean paste is small in floor area, and is suitable for large-scale industrial production; and thus, market demands for the Pixian thick broad-bean paste is satisfied.