An object detection method, comprising: obtaining (S110) an enclosing frame of a target object in an input image; according (S120) to the enclosing frame, determining a reference frame from a predetermined candidate frame set comprising a plurality of candidate frames; generating (S 130) a size-related feature according to a size of the reference frame and a size of the enclosing frame; and detecting (S 140) an object in the input image by applying the size-related feature in a machine learning model, wherein the generating (S 130) a size-related feature according to a size of the reference frame and a size of the enclosing frame comprises: determining a width ratio and a height ratio of the enclosing frame with the reference frame as the size-related feature, or determining a natural logarithm of the width ratio and a natural logarithm of the height ratio as the size-related feature; wherein the method further comprises: predetermining (S410) a relationship between respective candidate frame sets and respective object categories; determining (S420) an object category to which an object to be detected belongs; and selecting (S430) a candidate frame set according to the determined object category. obtaining (S110) an enclosing frame of a target object in an input image; according (S120) to the enclosing frame, determining a reference frame from a predetermined candidate frame set comprising a plurality of candidate frames; generating (S 130) a size-related feature according to a size of the reference frame and a size of the enclosing frame; and detecting (S 140) an object in the input image by applying the size-related feature in a machine learning model, wherein the generating (S 130) a size-related feature according to a size of the reference frame and a size of the enclosing frame comprises: determining a width ratio and a height ratio of the enclosing frame with the reference frame as the size-related feature, or determining a natural logarithm of the width ratio and a natural logarithm of the height ratio as the size-related feature; wherein the method further comprises: predetermining (S410) a relationship between respective candidate frame sets and respective object categories; determining (S420) an object category to which an object to be detected belongs; and selecting (S430) a candidate frame set according to the determined object category. determining a width ratio and a height ratio of the enclosing frame with the reference frame as the size-related feature, or determining a natural logarithm of the width ratio and a natural logarithm of the height ratio as the size-related feature; wherein the method further comprises: predetermining (S410) a relationship between respective candidate frame sets and respective object categories; determining (S420) an object category to which an object to be detected belongs; and selecting (S430) a candidate frame set according to the determined object category. predetermining (S410) a relationship between respective candidate frame sets and respective object categories; determining (S420) an object category to which an object to be detected belongs; and selecting (S430) a candidate frame set according to the determined object category. <EOS>