A method for determining a deviation in a wind alignment angle of a wind turbine, comprising: obtaining (S101) history operation data of a wind turbine within a time period, wherein the history operation data comprises ambient wind speeds, detected wind alignment angles, and output power that are at different moments in the time period; and determining (S102) the deviation in the wind alignment angle for a windspeed section, based on the detected wind alignment angle and the output power at a moment within the time period, wherein the ambient wind speed at said moment belongs to the windspeed section; characterized in that : determining the deviation in the wind alignment angle for the windspeed section comprises: determining the deviation in the wind alignment angle for an i-th windspeed section, based on average power of each angle section corresponding to the i-th windspeed section, wherein the i-th windspeed section serves as the windspeed section; wherein average power P ij of a j-th angle section corresponding to the i-th windspeed section is an average of output power at all the moments at each of which the ambient wind speed belongs to the i-th windspeed section and the detected wind alignment belongs to the j-th angle section; and wherein a predetermined windspeed range is divided into M windspeed sections with a first predetermined interval, a predetermined angle range is divided into N angle sections with a second predetermined interval, wherein i and j are integers, M ≥ i > 0, and N ≥ j > 0. obtaining (S101) history operation data of a wind turbine within a time period, wherein the history operation data comprises ambient wind speeds, detected wind alignment angles, and output power that are at different moments in the time period; and determining (S102) the deviation in the wind alignment angle for a windspeed section, based on the detected wind alignment angle and the output power at a moment within the time period, wherein the ambient wind speed at said moment belongs to the windspeed section; characterized in that : determining the deviation in the wind alignment angle for the windspeed section comprises: determining the deviation in the wind alignment angle for an i-th windspeed section, based on average power of each angle section corresponding to the i-th windspeed section, wherein the i-th windspeed section serves as the windspeed section; wherein average power P ij of a j-th angle section corresponding to the i-th windspeed section is an average of output power at all the moments at each of which the ambient wind speed belongs to the i-th windspeed section and the detected wind alignment belongs to the j-th angle section; and wherein a predetermined windspeed range is divided into M windspeed sections with a first predetermined interval, a predetermined angle range is divided into N angle sections with a second predetermined interval, wherein i and j are integers, M ≥ i > 0, and N ≥ j > 0. determining the deviation in the wind alignment angle for an i-th windspeed section, based on average power of each angle section corresponding to the i-th windspeed section, wherein the i-th windspeed section serves as the windspeed section; wherein average power P ij of a j-th angle section corresponding to the i-th windspeed section is an average of output power at all the moments at each of which the ambient wind speed belongs to the i-th windspeed section and the detected wind alignment belongs to the j-th angle section; and wherein a predetermined windspeed range is divided into M windspeed sections with a first predetermined interval, a predetermined angle range is divided into N angle sections with a second predetermined interval, wherein i and j are integers, M ≥ i > 0, and N ≥ j > 0. <EOS>