Fluorescence sensors for complicated molecules such as pesticides were paid much attention lately due to the merits of simple operation, high sensitivity and selectivity, and in‐situ detection. In this work, a novel fluorescent sensor for pesticide starane was prepared based on imidazolium‐decorated bis‐cyanostilbene macrocycle (IBM). IBM exhibited the obvious “turn‐on” fluorescence change from dark blue‐green to bright blue after sensing starane with the high sensing selectivity among 28 kinds of guests. The detecting limitation was as low as 0.011 μM, which was the lowest one in literatures. The sensing mechanism was confirmed as that starane was located in cavity of IBM based on the molecular interaction of multiple hydrogen bonds, π‐π stacking and hydrophobic interaction. The application experiments suggested that starane was examined well on test paper with good selectivity and was quantitatively detected in water samples, implying the good real‐time and in‐situ application potential for IBM on sensing starane in real environment and daily life.