This paper proposes a new method for evaluating RBCs deformability with a microfluidic chip. In this method, three constriction channels with different width and two bypass channels are placed in parallel in the microfluidic chip. The three parallel constriction channels with different width enable to observe the wide measurement range of RBCs deformation. And the bypass channels reduce the transit velocity of RBCs that pass the constriction channels. The experimental result with proposed method shows enhanced negative correlation between RBCs transit velocity and deformation. The results support that the proposed method provide clearer tendency about RBCs deformability compared with conventional method.