The invention provides a byproduct hydrogen purification recovery system and method in the chlorine industry. The byproduct hydrogen in the chlorine industry enters a washing tower, the solution in a water tank enters the spraying tube in the washing tower through a water pump at the same time, the hydrogen dechlorinated by the washing tower is discharged from the top of the washing tower and then enters a buffer tank, then the hydrogen buffered by the buffer tank enters a hydrogen compressor for pressurization and then enters a gas-liquid separator, after gas-liquid separation, the hydrogen enters a deaerator for removing the oxygen in the hydrogen, after deoxidization, the hydrogen enters a first adsorber for dehydration and impurity removal and then enters a gas filter, and finally after filtration, the hydrogen enters a hydrogen recovery device. The system provided by the invention simplifies the instrument and equipment and industrial processes, and saves industrial costs.