Portable detection of cancer cells is important for early-stage diagnostic applications and prognosis of cancer. Herein, a simple and sensitive chemiluminescence method was proposed for portable detection of cancer cells via a handheld luminometer. It is based on the cancer cell triggered cyclic strand displacement reaction (SDR) for signal amplification. Cancer cells, CCRF-CEM, bind to their aptamer and release the trigger DNA (TDNA) of SDR. The TDNA initiates the cyclic SDR between magnetic bead modified hairpin DNA 1 (MB-H1) and HRP-tagged hairpin DNA 2 (HRP-H2), resulting in an enrichment of HRP onto the surface of magnetic beads by forming H1/H2 duplexes. HRP catalyzed luminol/H2O2/PIP solution to produce a strong chemiluminescence (CL) signal. CCRF-CEM cells were sensitively detected by combining magnetic enrichment with the signal amplification of SDR. The CL intensity showed an excellent linear relationship with the number of CCRF-CEM cells in the range of 100 to 5 × 104 cells per mL. The detection limit was as low as 85 cells per mL. Therefore, it offers a sensitive, cheap and portable method for the chemiluminescence detection of cancer cells and provides a new option for the early diagnosis of cancers.