The invention provides an isolation protection device and construction method for preventing pile foundation reinforcement cage deflection, and belongs to a bridge construction auxiliary device in construction engineering and a construction method of the bridge construction auxiliary device. The isolation protection device comprises a guiding column, and a hook is arranged at the top end of the guiding column. The hook is shaped like an n. The construction method for preventing pile foundation reinforcement cage deflection comprises the steps that the guiding column stretches into a pile hole; the n-shaped hook is hanged on a steel casing; a reinforcement cage is installed in place; concrete is poured. The isolation protection device and construction method for preventing pile foundation reinforcement cage deflection have the advantages that the guiding column has the effects of guiding and isolation with the hole wall on the reinforcement cage, and in the pouring process, the reinforcement cage is not likely to deflect. Along with increasing of the poured concrete quantity, the torque becomes larger, the guiding column always exists to conduct isolation and guiding in the middle, it is guaranteed that on the condition that the torque becomes larger, deflection does not occur, the bending moment in the reinforcement cage is not accumulated to be too large, the phenomena that in the concrete pouring process, the reinforcement cage rotates left and right, swings to collide the hole wall, deflects and deforms can be effectively prevented, deflection control is stable and reliable, and the construction quality is guaranteed.