The invention discloses a circulating tumor cell assay instrument comprising a micro-fluidic chip, which further comprise a sample injection, a liquid collector, a signal acquisition and analysis system, a core controller, and a display control interface, the core controller is electrically connected to the sample injection, the signal acquisition and analysis system and the display control interface to control operation, the sample injection system is connected to the sample inlet of the micro-fluidic chip to drive a sample into the chip according to an instruction of the core controller, theliquid collector is connected to the sample outlet of the micro-fluidic chip to collect enriched target liquid and waste liquid, the signal acquisition and analysis system acquires and analyzes an electric response signal induced by the impedance change of a region with detection electrodes according to an instruction of the core controller, and the display control interface displays a data result according to an instruction of the core controller. The circulating tumor cell assay instrument does not need to mark cell, the processing throughput is high, high-purity living circulating tumor cells can be automatically separated out, the testing process is simple, the efficiency is high, and the application range is wide.