Enriching and isolating circulating tumor cells (CTCs) have attracted significant interest due to their important role in early cancer diagnosis and prognosis, allowing for minimally invasive approaches and providing vital information about metastasis at the cellular level. This review comprehensively summarizes the recent developments in microfluidic devices for CTC enrichment and isolation. The advantages and limitations of several microfluidic devices are discussed, and the design specifications of microfluidic devices for CTC enrichment are highlighted. We also developed a set of methodologies and design rules of label-free microfluidics such as spiral, deterministic lateral displacement (DLD) and dielectrophoresis (DEP) to allow researchers to design and develop microfluidic devices systematically and effectively, promoting rapid research on design, fabrication, and experimentation.