The invention relates to a method using lithium bentonite as a cement product additive and an application of the method using lithium bentonite as the cement product additive in cement product building materials. Natural calcium or sodium bentonite is taken to be dried, a lithium agent is added in parts by weight, water is added according to the material total ratio to mix and extrude, the mixture is fully mixed, then sealed, stored at 60 DEG C, dried and ground so as to obtain the lithium bentonite; and the lithium bentonite is added according to 0.3-3wt% of the crude cement usage of the cement product, and water is added so as to produce mud which is formed through a forming machine and is cured at normal temperature or in a steaming mode. The lithium bentonite is used as the additive to be added into the cement product, the dispersibility of the cement in the product can be obviously improved, the hydration reaction is complete and uniform, the early strength is greatly increased by above 20%, and the product performance is obviously improved. The production technology of the lithium bentonite is simple, raw materials are low in price and easy to obtain, and the lithium bentonite is simple and easy to be applied to the cement products.