The oxalate formation of the kraft pulp with different influence factors ( namely time,temperature,oxygen pressure and alkali charge ( NaOH mass fraction) during an oxygen delignification process was investigated by single-factor experiments.On this basis,the Box-Benhnken experiment of the response surface methodology was conducted to optimize the main factors influencing oxygen delignification.The results show that,under the condition of 0.2% MgSO4 and 10% pulp consistency,optimal oxalate formation conditions during the oxygen delignification are a temperature of 100℃,an alkali charge of 1.5%,a reaction time of 60 min and an oxygen pressure of 0.5MPa.Under the optimal conditions,the oxalate content is 0.25 g /L and the ratio of the Kappa number difference to the viscosity difference is 0.045.