The invention provides a preparation method of a visible sulfanilamide molecular engram detection membrane. The preparation method comprises the following steps: 1, preparing nano-crystalline cellulose; 2, synthesizing a sulfanilamide resin engram precursor polymer; 3, preparing a chiral nematic sulfanilamide molecular engram composite membrane; 4, preparing the visible sulfanilamide molecular engram detection membrane. In the preparation method, the liquid crystal cellulose being wide in source is taken as a detection substrate, and is subjected to room-temperature evaporation to assemble a regular nematic membrane structure; a molecular imprinting technology has a selective identification characteristic; a complex microcosmic signal is converted into a macroscopic visible signal to be applied to detection of pollution target molecules.