The invention provides a composite ceramic water reducing agent and a preparation method thereof. The method comprises the following steps: (1) adding tannin extract, bis-allyl polyglycol ether, acrylic glucose ester, unsaturated carboxylic acid and salt thereof as well as water into a reaction kettle, stirring and heating up; (2) adding an initiator into the reaction kettle when the temperature rises to 90-120 DEG C, maintaining the temperature to be within the range of 100-120 DEG C, and continuously reacting for 5-10 hours; and (3) adding an inorganic dispersing agent, stirring for 0.5-2 hours, then cooling and discharging to obtain the composite ceramic water reducing agent.