Cantharidin (CTD), an effective component of Chinese herbal medicine with unique efficacy, caused poisoning or death constantly for incorrect use. Therefore, there is an intense need for a reliable, selective, sensitive and low-costing analytical method for monitoring the concentration of CTD in biological samples. In this work, a ratiometric fluorescent sensor (CdTe@MIPs/CDs@NIPs) was successfully constructed for selective determination of CTD by simply integrated the non-imprinted polymers coated CDs (CDs@NIPs) with cadmium telluride quantum dots coated with molecular imprinted polymers (CdTe@MIPs). CDs@NIPs were directly used as reference signal without addition of CTD templates and the as-prepared CdTe@MIPs were response signal. With the CTD addition, the fluorescence intensity of CdTe@MIPs decreased, while the fluorescence of CDs@NIPs remained approximately unchanged, resulting a detection limit as low as 0.15 nM. By spiked human blood samples, the ratiometric sensor was successfully applied to CTD detection with good recoveries of 96.12–107.40% and relative standard deviation (RSD) of 2.87–3.96%. Moreover, after centrifuging and re-eluting, the developed sensor could be effectively recycled and reused five times. Significantly, the proposed platform with low-cost and highsensitivity opens a door towards the practical applications of ratiometric sensor and shows immense potential in pursuing the sensitive, reliable and low-cost determination of poisons in forensic toxicology analysis.