Desizing-scouring-bleaching-dyeing of cotton fabrics in one-bath was discussed in this paper. The appropriate reactive dyes, refined enzyme and H2O2 elimination agent and dyeing technology parameters were selected preciously and the optimum conditions were obtained: H2O2 (30%) 4 g/L, refined enzyme 2 g/L, Na2SiO3 2g/L, Peregal O 1 g/L, bath ratio 1:20, scoring and bleaching at 95°C for 45min. Then, adding sulfourea 12g/L, controlling pH 7, adding reactive red dye 3BS 3% in raffinate, dyeing at 35°C for 30min and fixing at 70°C for 30 min. Compared the one-bath process with the traditional one, the former can get similar performance on dyeing. In addition, the former shows such advantages as short time, high efficiency, low energy consumption and reduced sewage emission. “One-bath” dyeing process is a promising approach to replace the old one.