Using contour grouping to get perceptual objects from natural images is a traditional difficult problem in computer vision. To provide a cue combination model

which accords with human visual perception and the statistical of the natural images

is the key problem of the definition of grouping cues and the improvement of grouping quality. According to the conditions when a linear cue combination rule works

a cue combination model for contour grouping

which fits the ecological joint distributions of continuity and similarity in Gestalt cues

is proposed. The cue combination model helps to explain how two independent cue channels could give rise to the particular form of the joint distribution of two correlated cues. It also overcomes the cue combination problem between correlated cues which can't be resolved by discriminative model. The proposed model is a quantitative model of Gestalt cues which accords with the statistical of the natural images and human visual perception better.