The invention discloses a method for controlling the oxygen content of an outlet of an economizer for a W-shaped flame boiler. The method comprises the following steps: 1, under the conditions that the operation oxygen content of the boiler, the combustion coal category, the grinding operation mode, the air distribution mode and the like are not changed, actually measuring the oxygen content of the outlet of the economizer, and analyzing a deviation of the oxygen content; 2, analyzing the cause of the deviation of the oxygen content; 3, performing heating state adjustment on primary air; 4, adjusting the air distribution mode; and 5, adjusting the deviation of the powder content. According to the control method, the deviation of the oxygen content of the outlet of the economizer can be adjusted, so that the deviation of the oxygen content of the outlet of the economizer can be small as far as possible during operation of the boiler, the combustion in a furnace hearth is more uniform, and the boiler efficiency is improved.