The invention relates to a shield launching end combined reinforcing structure and a construction method thereof. The combined reinforcing structure comprises a high-pressure jet grouting pile vertical reinforcing region and a drill hole grouting horizontal reinforcing region, wherein the high-pressure jet grouting pile vertical reinforcing region is used for performing vertical reinforcement on ashield launching end; and the range of the vertical reinforcing region is a range being 15 to 20 m outside an underground continuous wall of a shield launching well and 3 to 5 m of the outer edge ofa shield tunnel structure in a horizontal direction, and being 3 to 5 m above the top of the tunnel and 3 to 5 m under the bottom of the tunnel in a vertical direction. The horizontal reinforcing region is inclined in the outer side horizontal direction or the horizontal direction or the downward direction from a shield launching end opening of the underground continuous wall along a shield excavation contour line. According to the method, a combined reinforcing structure is used for forming an L-shaped semi-enclosure structure, and the underground water erosion is isolated. The shield launching end combined reinforcing structure and the construction method are used for overcoming the defects of a single reinforcing structure of the shield end and improving the reinforcing effect of the shield launching end, and have the advantages that the structure is simple; the reinforcing quality is high; the construction efficiency is high; the cost is reduced; the time and the labor are saved; and the use effect is good.