Abstract: Forward imaging technique is the base of the combined method for density reconstruction with forward calculation and inverse problem solution. This paper proposes the idea of girding the areal source as many point sources. Using the blurring window as the affecting factor of the detector blur, the projecting matrix from any point source to any detector pixel with X-ray trace technique is obtained, the projection equation for the radiographic system with areal source blur and detector blur is introduced. The projection equation is used to gain the same deviation information about the object edge as the experimental image. The forward projection equation is combined with the constrained conjugate gradient method to form a full procedure of density reconstruction, which is applied on a simulated image of French Test Object and an experimental image. The results show that using the projection equation, the affecting range of the blur is decreased and can be controlled in one or two pixels.