When I add environment texture to world node my object shadow disappear.
Do I need to turn off background strength? I want to make my object to look like background so I lost shadow that I wanted
It is not that the shadow dispappears, but it is not as dark... Why? Because the environment will illuminate that area. Think of the environment as a giant sphere that surrounds the scene, emitting light from every pixel of the image texture used. So the question is: if you like the shadows without the world texture, do you really need it? Else just bring down the strenght.
If you want to light up your scene with an Environment Texture it depends on which render engine you are using.
If you use Cycles an
HDRI in the
Environment Texture node should do the job. It looks like you are using a PNG file. You can use HDRIs that are shipped with Blender or download them from https://hdrihaven.com for example. See How to use 2.8's default HDRi's in renders? for details. Switch to
Rendered view to see the shadows (Z). It doesn't show up in
Material Preview view.
If you use Eevee you need extra lights in your scene to have objects cast shadows because the Eevee renderer cannot use the light info of the HDR image. See How can I get HDRI shadows in an Eevee scene? for details.