The invention relates to a method for cooling peripheral frozen earth and preventing water catchment in an excavation pit for a permafrost region. The method is characterized in that a pit slot is excavated at a position which is 0.5-5 m far away from the rim of the designed pit; the slot depth is a depth being 0-100 cm below underground permafrost table; a cooling pipe is paved at the bottom of the pit slot; a waterproof film is paved on the cooling pipe, the bottom of the slot, and the wall of the pit to a ground surface, and refilled and punned with filled earth; and the cooling pipe injected with circular freezing liquid is connected with a refrigerator on the ground surface through a hose. Shown by practices, with the adoption of the method provided by the invention, the problems of melting and stability loss of the frozen earth and the frozen earth in the excavation pit in a warms-season construction process and water leakage and water collection of underground water can be solved through the effective combination of refrigeration and water insulation, so that the permafrost stability can be effectively protected, and the normal construction and the long-term stability of the Qinghai-Tibet direct-current networking engineering in the permafrost region can be ensured.