Abstract Circulating tumor cells (CTCs) have been widely considered as novel biomarkers for the clinical diagnosis of cancer. CTCs are the cells detached from the parent tumors and shed into the blood stream to initiate tumor metastasis. Although CTCs are rare, their detection in one’s blood sample is essential for cancer early diagnosis and for starting the treatment procedure. Here, we introduce a novel method for trapping CTCs using dielectrophores, which effectively employs pores of a replaceable porous membrane as CTC traps. The applied dielectrophoretic force efficiently traps and holds CTCs in a stable position and further enables us to perform various on-chip analysis with them. First, using finite element method, the performance of the system was simulated for different physical conditions. Then, the chip was fabricated and its trapping performance was experimentally validated. Cells were entered into the microchannel and trapped in the pores of a polydimethylsiloxane membrane. The proposed microfluidic chip is capable of detecting rare cells in a large cell population.