The invention belongs to the technical field of metallurgy and particularly relates to a preparation method of sheet billet continuous casting and rolling easy-acid washing hot rolling strip steel. The preparation method comprises the steps of: smelting liquid steel and continuously casting to form a sheet billet; heating the sheet billet; descaling the sheet billet by using high pressure water and finish-rolling the sheet billet, wherein during the finish rolling process, the water amount of cooling water between a first rack and a second rack is greater than or equal to 60%; the water amount of cooling water between the second rack and a third rack is 50%-60%; the water amount of cooling water between the third rack and a fourth rack and between the fourth rack and a fifth rack is 30-50%; and water amount of cooling water between the fifth rack and a sixth rack and between the sixth rack and a seventh rack is 10-20%; performing ultrafast cooling and laminar flow cooling on the finish-rolled sheet billet to finally obtain iron scale with the content of FeO lower than 10 wt%; and thinning the iron scale for 5-10 microns to obtain the easy-acid washing hot rolling strip steel in a uniform structure. According to the easy-acid washing hot rolling strip steel produced by the preparation method, the iron scale has a rational structure and good uniformity and the surface of the iron scale is provided with a plenty of micro-cracks; in the subsequent acid washing process, the acid washing efficiency of the strip steel is improved, acid consumption is reduced and acid washing efficiency is improved efficiently while the acid washing quality of the sheet steel is guaranteed.