I want to bake the light map and then I use MAX render to texture, get the VRayCompleteMap, and then in blender will give this map base color and mission, but I found that when I shrink the object or a distant observation model, the model will appear black lines, and then I found that this is my cut UV lines, I want to ask what can be done to eliminate these black lines?
What you called UV line is named “seams”. And you see black pixels when moving away of your object due to mipmapping (engine use a reduced size of the texture so as to free some VRAM), and also the lack of pixel color stretching around your UV islands (here a quick and nice explanation from Painter doc).
First task to do is to not use a flatten mapping, but a manual unwrap, to get control about your seams placement, and keep enough space between your UV islands.
If I remember well, pixel bleeding is handle by this parameter on the Render To Texture popup:
2 is quite low but OK if your texture is small (like 256px²), it’s up to you to see what value seems the right to fit, depending of your unwrap.