An apparatus for determining ambient illumination in an AR scene includes: setting virtual light source points in an AR scene, predicting reference illumination parameters of all of the virtual light source points for a current image frame according to a neural network, configuring a reference space confidence and a reference time confidence for the virtual light source points, acquiring a reference comprehensive confidence by fusing the reference space confidence and the reference time confidence, acquiring a fused current comprehensive confidence by comparing the reference comprehensive confidence with a comprehensive confidence of a previous image frame, acquiring illumination parameters of the current frame by correcting the illumination parameters of the current image frame according to the current comprehensive confidence, the previous frame comprehensive confidence and the previous frame illumination parameters, and performing illumination rendering of a virtual object in the AR scene according to the illumination parameters of current frame.