In this paper, the effect of the volcanic ash dyed on cotton knitted fabrics was studied in various ways. A cationic agent was used to improve the depth of color of the fabric in the dyeing process. K/S values of dyed fabrics were measured to examine the dyeing properties. Cationic agent pretreatment, followed by dyeing with volcanic ash, was tested. In the dyeing experiment, the effects of a wide range of parameters such as the concentration of cationic agent, treatment time, treatment temperature and treatment pH of the dyebath were studied. Experimental results showed that the pretreatment with cationic agent improved the dyeing properties of cotton knitted fabrics with volcanic ash. At this point, concentration of cationic agent was 4%(on weight of fabric), treatment time was 40minutes, treatment temperature was 80 C and treatment pH of the dyebath was a neutral condition.