The invention discloses a cutter head connecting structure and a reconstruction method thereof. The cutter head connecting structure comprises a cutter head and a transmission shaft, wherein an internal spline is arranged in the cutter head, a blind hole which is coaxial with the internal spline is arranged at the inner end of the internal spline, a spline is arranged on the transmission shaft, is embedded into the internal spline and is engaged with the internal spline, and an auxiliary shoring cylindrical rod which is coaxial with the transmission shaft is arranged at the end part of the spline, extends into the blind hole and is in clearance fit with the blind hole. According to the cutter head connecting structure and the reconstruction method thereof, the radial load bearing of the spline part is achieved through arranging the auxiliary shoring cylindrical rod and the blind hole, the condition that the load bearing of the spline is uneven due to a cantilever is avoided, and the condition that the spline part is uniform in load bearing and stress is ensured, so that the damage to the spline position of equipment is avoided, the service life of the equipment is greatly prolonged, the maintenance is reduced, the maintenance cost is reduced, and the production efficiency is increased greatly; the cutter head connecting structure also has the characteristics of simple structure and low cost.