So after I imported my mesh, there is this weird line all over my mesh . but when I zoom in, the line disappear
Studio can be VERY buggy when it comes to meshes, it’s really not anything you can fix as far as I’m concerned, though it might just be some texturing issue? Maybe you could try using the mesh without a texture and see how it appears, if it’s still the same then it’s a studio issue.
Those lines appear because the UV map is rendered slightly less accurately the further away the camera is from the object—try filling in the image texture beyond the boundaries of your UV map, like this:
Notice that the texture extends far beyond the bounds of the UV map (denoted by red lines). If you push the black background in your texture further away from the edges of your UV, the lines will become less and less apparent until eventually disappearing if you leave enough space