The invention relates to a protection method for a tunnel shield to laterally penetrate in an existing high-speed railway pile foundation. The protection method comprises the following steps: (1) making an on-the-spot survey, and determining the soil layer and the hydrogeological condition of the construction area; (2) understanding the surrounding engineering environment and determining buildingsto be protected; (3) determining the diameter, the length and the spacing distance of isolation piles according to the depth of a shield tunnel; (4) drilling holes, pouring isolation piles, arrangingcorresponding ground crown beams, and forming a frame structure through the isolation piles by using supporting beams; and (5) organizing construction machinery and appliances to enter a site for construction.