A series of indole-based poly(hexahydrozine) (IN-PHT) flexible film materials were prepared by simple copolymerization of tryptamine (Tryp), poly(propylene glycol) bis(2- aminopropyl ether) (D- 400) and paraformaldehyde, and the films were soaked in MgCl₂ solution to prepare the Mg-poly(hexahydrozine) (Mg-IN-PHT) films crosslinked by Mg²⁺-indole interaction. The uniform distribution of Mg²⁺ in Mg-IN-PHT was confirmed by EDS. The formation of cation-π interaction between Mg²⁺ and indole was demonstrated by UV, RF and theoretical calculation. The mechanical properties of Mg- IN- PHT films were characterized by cyclic tensile test. The results indicate that Mg- IN-PHT films have the stronger tensile strength (16.1 MPa) and toughness (206.2%), which are significantly higher than IN-PHT films (11.0 MPa, 117.0%). On the one hand, cation- π cross-linking increases the cross-linking density, thus enhancing the strength of film; on the other hand, the molecular chains of flexible polymer network slip easily when it was externally stimulated. So that the "point- surface" cation- π interactions could be formed and released more easily, and the energy dissipation effect is better, thus the toughness of film is improved. In addition, the thermal stability of Mg- IN- PHT was also investigated. The results indicate that the thermal decomposition temperature (280 ℃) and Tg (-10 ℃) of Mg-IN-PHT films are higher than those of IN-PHT films (234℃ ) and (- 16℃ ). Finally, the dynamic “point- surface” cation- π interaction endows Mg- IN- PHT films with excellent self-healing and recycling abilities.