Traditional spatial concealment effect is described by Weber law. However， it only considers photopic vision， and can not fit to weaker or stronger light intensity. In order to depict spatial concealment effect more effectively， a novel fitting formula was proposed only by signal processing method. Several different models is used to fit the data in Konig and Brodhun in experiments， and the fitted results demonstrate that the root mean square error of the proposed model is only 0010 2， which is less than those of traditional Weber law， superior form of Weber law， Guilford model， and Chen model. It can be concluded that proposed model can fit to human eyes in more expansive range of light intensity， and can be applied to engineering practice more widely.