The invention provides a method for the combined treatment of wastewater by utilizing waste liquor during the production of synthetic ammonia-methynol. The method compromises the following steps: feeding the wastewater generated during the production of synthetic ammonia after being filtered, deposited and coagulated into a primary denitrification tank, and adding methanol residual liquid and phosphate salt to the primary denitrification tank for denitrification; then feeding the wastewater into a nitration tank, adding alkali wastewater with the pH value being adjusted to 8 to 9 in the nitration tank for nitration, and further feeding the wastewater into a secondary denitrification tank; and finally recovering and reutilizing or directly discharging the wastewater after being subjected tomembrane separation and filtration. The methanol residual liquid comes from a methanol rectification section during the production of the synthetic ammonia-methynol; and the alkali wastewater comes from the regeneration phase of anion exchange resin during the production of soft water. By adopting the method, the treatment cost of the wastewater is greatly reduced, and the harm of industrial waste liquid to environment is further reduced simultaneously, thereby changing the waste into valuables, realizing the re-utilization of resources, complying with the sustainable development strategy, and having higher economic benefit and social benefit.