The invention discloses a self-heating gas generation foam fracturing fluid and a preparation method thereof. The fracturing fluid is prepared from the following raw materials in percentage by mass: 0.2%-0.5% of a thickening agent, 0.2%-0.5% of a cross-linking agent, 6%-8% of sodium nitrite, 6%-8% of ammonium chloride, 0.7%-1% of a heating catalyst, 0.1%-0.3% of a breaking aid, 0.1%-0.3% of a gelbreaker, and the balance of water. The thickening agent is acid-resistant modified guanidine gum. The fracturing fluid has good gel breaking performance, can automatically generate heat, generate gasand increase pressure, is foamed on site, greatly reduces requirements for ground equipment, has plugging and profile control effects higher than those of conventional foam, has low filtration loss and good sand carrying performance, achieves gel breaking through the low-temperature gel breaker, can promote flowback of the gel breaking fluid, and has good application prospects. The fracturing fluid is suitable for fracturing transformation of middle-shallow-layer high-condensation-point oil, thick crude oil and low-temperature low-pressure low-permeability oil and gas reservoirs.