The SmCo/Cr films have been prepared with the help of DC magnetron sputtering method. The structure of Cr underlayer depended on several sputtering factors, and directly influenced the coercivity of SmCo/Cr films. The orthogonal design of experiments and mathematical statistical method are considered as the effective methods to optimize sputtering condition of Cr underlayer for high coercivity of SmCo/Cr films. Using the orthogonal design method, the effects of the four factors, such as, the target-substrate distance, the DC power, the sputtering pressure and the sputtering time were simultaneously investigated by only 9 experiments. The optimal condition of Cr underlayer was obtained, that is 4 cm in T-S distace, 50 W in DC power, 0.5 Pa in sputtering pressure, 9 min in sputtering time. The target-substrate distance, the DC power and the sputtering pressure are very important factors for coercivity, on the other hand, the effect of sputtering time is not obvious. It can be proved that our orthogonal design of experiment is of 95% confidence.