The invention relates to a method for bleaching through a low-temperature cashmere bleaching agent. A metal salt solution contains 1% fatty acid methyl ester ethoxylate sulfonate, and an oxidation bleaching solution comprises 15g/L of 30% hydrogen peroxide, 8g/L of tetraacetylenediamine, 3g/L of glucose, 2.5 /L of trisodium phosphate, and 0.5g/L of ethylene glycol monobutyl ether; a reduction bleaching solution comprises 3g/L of thiourea dioxide, 1g/L of iso-tridecanol polyoxyethylene ether, 1g/L of glucose, 2g/L of sodium silicate, and 1g/L of sodium sulfide. By adopting the low-temperature cashmere bleaching agent and the bleaching method thereof, the whiteness of cashmere can be effectively improved, the damage on the cashmere can be alleviated, and the yellowing index of the bleached cashmere is low.