In this paper, the dyeing ability of the volcanic ash dyeing on cotton knitted fabrics were investigated. Acrylic copolymer was used to improve the depth of fabric color in the dyeing process. K/S values of dyed fabrics were measured to examine the dyeing properties. Two different classes of dyeing process were tested; (1) volcanic ash dyeing after pretreatment and (2) simultaneous co-treatment with volcanic ash and acrylic copolymer. In the first process, the effects of parameters such as the concentration of volcanic ash, concentration of Na2S04, dyeing time, dyeing temperature and pH of dyebath were noted. In the second process, the effects of parameters such as concentration of acrylic copolymer, dyeing time and temperature, and drying temperature were noted. Experimental results showed that the co-treatment of acrylic copolymer improved the dyeing properties of cotton knitted fabrics with volcanic ash. For the first dyeing experiment, concentration of dispersing agent was 0.1%, concentration of volcanic ash was 4%, treatment time was 20minutes, concentration of $Na_2SO_4$ was 2%, treatment temperature was $60^{circ}C$ and treatment pH of dyebath was neutral. In the second dyeing experiment, concentration of acrylic copolymer was 2%, treatment temperature was $80^{circ}C$, treatment time was 40 minutes, and treatment drying temperature was $150^{circ}C$.