The invention provides a pentiptycene conjugated polymer, a preparing method thereof and application thereof to rapid detection of nitroaromatic explosive. The general structural formula of the conjugated polymer is shown in the formula I. The conjugated polymer with pentiptycene segments is obtained efficiently through a Sonogashira coupled reaction, and the rigid pentiptycene structure has sufficient holes to form molecule channels, so that the electron-rich polymer responds to electron-deficient nitroaromatic molecules easily through electrostatic interaction, and extremely high sensitivity is revealed. The pentiptycene conjugated polymer has higher molecular weight and is higher in selectivity and sensitivity, and red shift of emitting wavelength is more obvious. The response time of the polymer is shortened by 2/3 compared with that of a polymer reported by a Swager set. The conjugated polymer can recognize the nitroaromatic explosive in a gas phase fast with high selectivity.