now it is last thing in my first project in blender. I made the model below in images and I thought everything is going well until I rendered it then I saw the quality is bad around the object that I built? Is there any thing that I must do in render to have better result? I will attach blender file to take a look.
Your compositing nodes are the cause. Because the blend does not have textures packed, I'm not 100% sure why you are compositing it the way you are.
However to fix the harsh edge around the container, simply check the Anti-Aliasing check box on both of the ID Mask nodes.
Here is what the mask looks like Anti-Aliased on the left, and without Anti-Aliasing (how you have it now) no the right.
Use a higher resolution. Maybe even use a "Dilate/Erode node" to blur the edges of the object. I'm not sure this will yield good results though. Mainly, just use a higher resolution for the render.
Set your Objects pass index to be a number( example: 2) Then enable the Object Index pass in the passes tab. Render again. Now put your object's mask (the first ID mask node) and pass it through a Dilate/ Erode node with these settings. Then subtract the original mask from this and you will have the edges of your model. Now put them through the blur node with the settings that you want. I hope you get good results.