The invention discloses an environment-friendly preparation method of a sulphur dye solution. The preparation method includes the following steps that water is added into a sulphur dye, beating is conducted, turbid liquid is prepared, the turbid liquid, a transition metal catalyst and sodium hydroxide are added into a high-pressure reaction kettle, air in the reaction kettle is replaced with nitrogen first, then hydrogen is introduced, and catalytic hydrogenation reaction is conducted at certain temperature and pressure. After reaction ends, temperature is reduced to normal temperature, hydrogen in the kettle is exhausted and replaced with nitrogen, an anti-oxidization agent is added, raney nickel or the transition metal catalyst is removed through filtering, and the sulphur dye solution is obtained. The method overcomes the defects that in the prior art, environmental pollution occurs, a large number of side products exist, purity is not high and cost is high, and the yield is high.