The invention relates to a preparation method for a fluorescent colorimetric chemical sensor and application of the fluorescent colorimetric chemical sensor in gas detection. The invention is characterized by adopting a simple, efficient and process-controllable electrostatic spinning method for preparing the fluorescent colorimetric chemical sensor and provides application of fluorescent colorimetric chemical sensor in the detection and alarming for organic volatile gases (VOCs). The metalloporphyrin/nano-porous fibrous membrane prepared according to the method provided by the invention is wide in VOCs detection scope; the fluorescent colorimetric chemical gas sensor provided by the invention is reusable and has the advantages of high sensitivity and quick response; the adaptive scope for environment humidity is wide and is 10-90%; the color change is visible by naked eyes; the preparation method has wide application prospect in the fields of microelectronics industry, spinning, pharmacy, environmental protection, chemical engineering control, domestic alarming, food preservation, aerospace, public security, custom, and the like.