The three composite boards which were made of continuous basalt fiber (CBF) and polypropylene fiber (PP) in different fiber ratios were researched on this paper. The manufacturing forming process included blending, carding, web formation, laminating and compression molding orderly. The tension and bending properties were investigated experimentally, and then dual variance analysis was used to show the significant difference of the mechanical property in the transverse and longitudinal orientation as well the appreciable impact of different fiber ratios to the mechanical property. The results show that the difference of the tension and blending strength in the same direction, among composite boards in different fiber proportions, is about 1~10Mpa; the difference in the same fiber proportion, between transverse and longitudinal, vary within a wide range from 10Mpa to 30Mpa. The results of variance analysis have also proved the conclusion, the difference between transverse and longitudinal is more significant than the difference among different fiber proportions. In the similar study, the significance hadn’t been seen sufficiently, so this paper provides reference to the actual application of the composite board.