Metasurfaces, a type of metamaterials with ultrathin thickness, have drawn tremendous attention in recent years due to their extraordinary flexibility to manipulate the light at subwavelength scale. It is useful in implementing various optical functions with a set of elements. A typical application of the metasurface is the holographic imaging, and one key parameter for the realization of holographic imaging is its optical efficiency. In this paper, we demonstrate the optimized holographic imaging by using the metasurface coded with a combined phase distribution. Firstly, the phase hologram is generated by Gerchberg-Saxton (GS) algorithm and the blazed grating is formed by introducing a periodic linear phasegradient distribution. Then the phase profile of the hologram is superimposed with the phase of blazed grating to generate a new phase distribution. Benefiting from the advantage of high efficiency for the desired light-manipulation, the metasurface based on the metal-insulator-metal (MIM) structure with different geometric parameters was utilized to cover the phase shift of 0 to 2π for encoding the generated phase distribution. The structure consists of a four-level quantized metallic Au nanorods elements separated by dielectric layers of SiO2 with the Au substrate, so a macro cell of our metasurface consists of 16 (=4× 4) subwavelength meta-atom, which are made of the Au nanorods with different width. The simulated far-filed patterns are calculated by finite-difference time-domain (FDTD) method. Compared to previous metasurface, our structure preferentially steer incident energy into the desired first order diffracted beam with the help of the equivalent of the blazed grating. And the optimized holographic imaging results could be achieved.