Abstract: Slope error and evaluation criteria of bent mirror of synchrotron radiation induced from gravity are introduced.According to the bending theory of beam, a method of gravity compensation by couple combined with multi-point forces is proposed.Taking the bent mirror of the XAFS beam-line (BL14 W) at Shanghai Synchrotron Radiation Facility (SSRF) as an example, the minimum root mean square (RMS) slope error of the bent mirror under the action of two-point, three-point and fourpoint forces combined with couples are calculated, and the result is 0.092, 0.041 and 0.022μrad, respectively.The comparison between the compensation results shows that when a couple is applied to both ends of the mirror, the corresponding compensation forces decreases, and the slope errors of the couple combined with two-point, three-point and four-point forces are 52%, 61%and68% of those without couples.Obviously, the compensation method of couples combined with multi-point forces is better than the multi-point forces compensation method.