The invention relates to a surface roughness measurement method and a realization device. The method is characterized by using a high-resolution microscopic camera which is equipped with a long objectdistance microscopic lens to shoot the surface image of a measured object when a single point light source irradiates, wherein after n point light sources are successively lightened, the camera can shoot n surface images I1-In, and the n is greater than or equal to 3; using a high-light black ball to calibrate the direction of the light source and acquiring the unit direction vector L1-Ln of allthe light sources and the transformation ratio coefficient f of a world coordinate (x, y, z) and an image coordinate (u, v); calculating the image coordinate value W(u,v) of a surface depth through the unit direction vector L1-Ln of the light source and the two-dimensional image I1-In of the surface of the measured object; acquiring the world coordinate value Z(x, y) of the surface depth of the measured object through the transformation ratio coefficient f; selecting the appropriate sampling length lr, and sampling the Z(x, y) to acquire a contour curve z(x); using a gaussian filter to filterthe contour curve z(x) so as to obtain a gaussian center line w(x), and separating a roughness profile r(x); and calculating the arithmetic average deviation value of the roughness profile r(x) and taking as the measured value of roughness.