Abstract: In northern Shaan gas field, the oil content, iron content and suspended solid concentration are relatively high and pipelines corrode and scale seriously. The main problems of mixed gas and sewage water samples in many blocks were analyzed. The sewage treatment process was optimizated by chemical oxidation-corrosion and scale flocculation treatment methods. The results showed that under the conditions of oxidation time of 10 min, NaClO of 40 mg/L, pH of 7.5, PAC dosage of 50 mg/L and PAM dosage of 2 mg/L, the quality of gas field sewage after the new sewage treatment process could meet the standard SY/T 6596-2004 《gas water reinjection method》. When corrosion inhibitor DW-1 dosage was 25 mg/L, the corrosion rate of the pipeline in the sewage could reduce to 0.021 1 mm/a, the inhibition rate could reach 86.25% and the scale inhibition rate could reach 98.17%. The new sewage treatment process solved the problems of scaling and corrosion.