The invention relates to a method for preparing a hybrid porous layer open tubular column through an in-situ ring-opening polymerization reaction. The method comprises mixing an epoxy group-containing functional monomer, an amino crosslinking agent and a pore-foaming agent, carrying out ultrasonic dissolution, introducing the solution into a capillary column and preparing the hybrid porous layer open tubular column under heating conditions through a ring-opening polymerization reaction. The method is easy to operate and has a fast reaction rate. According to different application requirements, hybrid porous layer open tubular columns having different inner diameters are prepared. Through use of different concentrations of the functional monomers and amino cross-linking agents, a series of the hybrid porous layer open tubular columns having different physical and chemical properties can be prepared.