The invention relates to a double-cavity pigtail drainage tube with a lock-in line system. The drainage tube includes a guide tube fixing base, a lock-in line connection base which is fixed on the guide tube fixing base, a locking pressing block and a flushing cavity; the drainage discharge end of the pigtail drainage tube passes through the guide tube fixing base and the lock-in line connection base in sequence, a lock-in line fixing shaft stretching outward is arranged on the lock-in line connection base, and a shaft hole is formed in the lock-in line connection base; the locking pressing block includes a shell and a rotation shaft connected with the shell, and the rotation shaft is installed in the shaft hole and rotate about the shaft hole, one end of a lock-in line passes through the guide tube fixing base and the lock-in line connection base in sequence and then is connected with a pull line ring; the flushing cavity includes a liquid inlet and a liquid outlet, and the liquid outlet passes through the guide tube fixing base and then is communicated with the pigtail drainage tube. The drainage tube can seal the lock-in line and the pull line ring completely and is connected with a flushing cavity channel, so that the drainage tube has a separate channel for water injection flushing, moreover, secondary infection caused by the gas-leakage liquid-leakage phenomenon can be effectively prevented, and the drainage tube is safer and more reliable.