Is it possible to bake normal map from high poly object without the existence of a low poly object?
Yes. You just need to ensure that you have an image texture assigned to the object and that the object has a UV map.
In it's simplest form, using Cycles:
- Split your screen so you can see the 3D view and a UV/Image Editor
- Create a new image in the image editor. Let's call it "BakedNormalMap"
- Switch back to your 3D view and select your hi-poly object
- Make sure you've unwrapped it and it has a UV map.
- Add a new material
- Click the dot at the end of the Color option and choose Image Texture (this can be achieved with the node editor if you prefer)
- Select your BakedNormalMap as the image
- Switch from the Materials tab to the Render tab and scroll to the bottom to find the Bake options
- Choose the Normal option and below this in the "Normal Settings" choose Space: Object
Don't forget to save your file.