AbstractSome pulp mills expect to produce viscose fiber by means of pre-existing pulp production lines as used for conventional kraft pulp having a relatively high content of hemicellulose. In the present study oxygen-reinforced alkali extraction was used to dissolve the oxidized lignin, which increased the content of alpha cellulose and increased the degree of mercerization. This paper considers the influence of alkalinity, time, temperature, oxygen pressure, and borax additive on oxygen-reinforced alkali extraction. According to the experimental results, the optimal oxygen-reinforced alkali treatment conditions were 120 g/L alkali for 30 min at a temperature of 40 °C. Single factor experiment results showed that oxygen pressure was beneficial to the process of alkali extraction, and 0.4 Mpa was selected as the optimal oxygen pressure. Kappa number, alpha cellulose, carboxyl content, and degree of polymerization (DP) were 1.2, 99.18%, 0.00965 mmol/g, and 1505, respectively, under the optimal reaction conditions. Results for the oxygen-alkali treatment showed that borax was important for affecting DP and the amount of cellulose II. DP was decreased to 1282 and the amount of cellulose II was increased to 36% when the borax was added.