The invention relates to preparation and application of a low-hydrocarbon anhydrous fracturing fluid crosslinking agent for unconventional reservoirs. The crosslinking agent is mainly composed of the following substances in parts by mass: 15-35 parts of main agent, 2-4 parts of phase-transfer catalyst, 7-12 parts of crosslinking accelerator and 40-58 parts of deionized water. The preparation of the crosslinking agent comprises the following steps: adding a certain proportion of deionized water into a reaction vessel, and heating to 60-70 DEG C; adding the phase-transfer catalyst and main agent, and stirring to perform homogeneous reaction; and cooling to room temperature, finally adding the crosslinking accelerator, and stirring to react for 15 minutes. The anhydrous fracturing fluid crosslinking agent has the advantages of high crosslinking speed with the gelatinizer and high gel stability; and the fracturing fluid system has high temperature resistance and shear resistance, and has ideal fracturing effects on high-temperature reservoirs.