The invention aims to provide an anti-cracking edge structure of a vehicle expansion kettle and a fusion method thereof. The structure comprises an expansion kettle; the edge of a kettle body of the expansion kettle is set as an anti-cracking return structure; the edge of the expansion kettle is divided into two edges; one edge is a return hook, and the other edge is set as a straight piece of a kettle body of a vertical expansion kettle; the straight piece is corresponding to the return hook in size; through the return edge structure, the edges of two sides of the expansion kettle are suffered from mutual containing effect during connecting and bonding to prevent cracks and openings in the bonding places; and through the return structure in the connecting place and the treatment of temperature rise, the connecting strength in the connecting place is reinforced, the gaps are reduced, the air tightness in the connecting place is increased, the service life is prolonged, the replacement rate is reduced, and the cost is reduced.