Does anyone knows how to remove these jagged lines from circle extrusion, I want smooth circle

This is an artifact of part tessellation used for rendering (displaying the shading, etc). So don't worry, your actual part is smooth, so if that's all you care about, you can ignore the jaggedness. Onshape tries to strike a balance between realism, and performance here, but sometimes it's not exactly what you'd like. In that case, you can do as Neil suggests above and change the tessellation quality, but again, it won't change your actual part, it will just make it look more smooth, but it will also slow things down a bit, which can become an issue on complex models.