Abstract: In an embodiment, a chip is used for isolating RBC from a whole blood and includes an accommodating space, a porous membrane and a microchannel system. The accommodating space is configured for containing a whole blood sample including RBC debris. The porous membrane is disposed at a bottom of the accommodating space and includes a plurality of pores. A diameter of the pores is larger than a size of the RBC debris and larger than a mean diameter of WBCs and CTCs. The microchannel system includes a liquid inlet, a liquid outlet and a microchannel. The microchannel is disposed between and communicates with the liquid inlet and the liquid outlet. The microchannel is disposed under the porous membrane.