A method to measure the grating parameters with the incident efficiencies ratio from both sides of the grating with the same wavelength is proposed. The proposed method has a higher precision than the original approach with the diffraction orders of m=±1 efficiencies ratio from one side of the grating. Firstly, by comparing the sensitivity of diffraction efficiency ratio to surface roughness under the condition of one side incidence and two-side incidence, it is found the former is more sensitive than the latter; secondly, the sine surface grating parameters are simulated for two-side incidence; finally, the volume phase holographic grating parameters are obtained experimentally more accurately. Meanwhile, the new method retains the advantage of the original method, such as no damage, simplicity and low cost.