Extra Texture on Screen

Unity Engine
1

I use Graphics.DrawTexture to draw the texture on OnGUI function. But I cannot find out why there is an extra line come up. My background building is fbx file, is there anyone can help to find out why? Or i miss out anything?

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2

i think the line may be come up by sky box

3

Thanks your reply , parandham03. I tried to change all camera to solid color instead of skybox, but there is no any effect.