The invention discloses 450MPa economical type high-surface-quality highly-reamed steel and a preparation method thereof, and belongs to the technical field of ferrous metallurgy and calendaring. The450MPa economical type high-surface-quality highly-reamed steel comprises, by weight, 0.045-0.085% of C, 0.30-0.80% of Si, 0.60-1.30% of Mn, 0.010-0.020% of P, 0-0.003% of S, 0.010-0.050% of Alt, 0.0010-0.0050% of Ca, 0-0.0050% of N, 0-0.0040% of O, and the balance Fe and inevitable impurities, wherein C*Mn*104 is smaller than or equal to 0.10, {P+10*S}*102 is smaller than or equal to 0.04, and Ca / S is greater than or equal to 0.3. The preparation method comprises the following steps of smelting, continuous casting, heating, rough rolling, hot box coiling, finish rolling, laminar cooling, coiling, slow cooling, acid pickling and coiling. The 450MPa economical type high-surface-quality highly-reamed steel has the characteristics of being low in cost and excellent in performance, and can meet the requirements of steel for car chassis and complex stamping parts.