Timely discovery and detection of pathogenic factors (i.e., circulating tumor cells) are of great significance for early diagnosis and therapy of tumorigenesis and metastasis, which gives the emergence of developing a way for rare cell biosensing. In this paper, we reported a dynamic electrochemical biosensor enabling specific capture, rapid detection and noninvasive release of target tumor cells. The biosensor was fabricated by grafting phenylboronic acid (PBA)-containing polymer on ITO-glass following with reversible immobilization of tumor cell targeting molecules via sugar-responsive PBA-catechol dynamic covalent chemistry. We found that the dynamic electrochemical biosensor showed a nice linear relationship between the captured cell densities and impedances (or currents) by EIS (or DPV) methods. Moreover, a high detection sensitivity with minimum detection limit at 3 cells mm^-2 was observed for target tumor cells (for example MCF-7 cells). Further study in a mixture of MCF-7 and HepG 2 cells revealed that, the number of detected MCF-7 cells shown no statistical difference compared to those of fluorescent labelling and counting method. Besides the good selectivity, the sugar-responsive molecular binding on the biosensor enabled noninvasive cell collection with a high viability over 87.2 %. In short, our dynamic electrochemical biosensor represents a promising platform for specific tumor cell detection and monitoring the cell capture and release, which paves the way for future diagnosis of early discovery and detection of tumorigenesis and metastasis.