The invention discloses an anti-seepage and leak-blocking construction method for excavation of a subway foundation pit in a soft soil area, which comprises the following steps: 1) joint pre-reinforcement construction of an underground continuous wall: constructing a pre-reinforcement structure of a high-pressure rotary jet grouting
pile, guiding holes, grouting by a
sleeve valve pipe, sealing the holes, guiding the holes again and pre-burying the
sleeve valve pipe for standby; and 2) the excavation of the foundation pit and the anti-seepage and leak-blocking construction: using surface floating earth for clearing and using the encased steel plate reinforcement method for anti-leak treatment for the situations that joints of the underground continuous wall have defects definitely and risk points are positioned below the excavation surface of the foundation pit, adopting the hole-guiding
cyanogen injection condensing method for blocking of leak points with slight
water leakage situation, adopting the horizontal hole grouting method for blocking for the
water leak points with serious
water leakage situation, and carrying out filling, grouting and reinforcement through the pre-buried
sleeve valve pipe after completing the blocking. The method has reasonable design, convenient construction, comprehensive consideration, good anti-leak and leak-blocking effect, fast leak-blocking speed and can solve the problems of pipe blocking, poor anti-leak and leak-blocking effect, slow construction progress and the like in the existing anti-leak and leak-blocking construction.