This paper presents a method for designing and predicting the flexural behavior and capacity of concrete beams with mixed CFRP-GFRP bars. The design of the section with CFRP-GFRP bars is expected to obtain better performance in serviceability and deformability comparing with the section with only CFRP bars or GFRP bars by realizing successive rupture of CFRP and GFRP bars in the section. The corresponding equations are proposed to calculate the flexural capacity, strain and stress of the section. The calculating values of flexural capacity are compared to existing test results and it is found that the calculating values are in good agreement with the experimental results. Further analysis on a calculating example shows that the section with CFRP-GFRP bars designed appropriately presents excellent performance.