The invention relates to a fracturing fluid cross-linking agent and a preparation method and application thereof. The cross-linking agent prepared by the invention can rapidly react with dialkyl phosphate, so that gelled fracturing fluid is formed by lower alkanes. The preparation method of the cross-linking agent comprises the following steps: (1) preparing a complex solvent, namely mixing an alcohol and water according to the mass ratio of 1:2-1:4, stirring uniformly, thereby obtaining the complex solvent; (2) sequentially adding the following components in parts by mass into a reaction container: 40-70 parts of the complex solvent, 30-60 parts of a trivalent iron salt and 6-25 parts of a complexing agent, and stirring and reacting at the temperature of 50-70 DEG C for 3-4 hours; and (3) cooling the reaction solution to the temperature of 30 DEG C, adding 2-8 parts of a cross-linking accelerator, uniformly stirring, thereby obtaining the lower alkane anhydrous fracturing fluid cross-linking agent.