The invention discloses a detoxifying process for barite thermal-reducing and water-leaching barium slag. The detoxifying process comprises the following steps of: enabling barium slag obtained afterbarite thermal-reducing and water-leaching to be in contact with a solution containing sulphurous acid; converting soluble barium in the barium slag into barium sulfate or/and barium sulfite; converting sulfur ions into elemental sulfur; and filtering to obtain a detoxified solution and detoxified barium slag. The detoxified barium slag is further in contact with air, so that barium sulfite in thedetoxified barium slag is completely converted into barium sulfate, in other words, the obtained detoxified barium slag is dried in air for several days, and is ensured to be converted into common solid waste from dangerous solid waste; SO2 is led into the detoxified solution or sulfite and acid can be added for regenerating the detoxified barium slag which is returned to a detoxifying process for being recycled. Especially, tail gas generated by a byproduct sulfur in a barium carbonate production process is used as a regenerating agent of the detoxified solution, so that the barium slag detoxifying problem is effectively solved, and purifying cost of the tail gas is remarkably reduced, and therefore, the purpose of combating poison with poison is achieved, and double benefits are achieved. The process has the characteristics of being simple and convenient to operate, clean and environmentally friendly, economical and efficient, and the like, and is suitable for industrial productionof barite thermal-reducing and water-leaching barium slag detoxifying.