I deployed my hub by docker service and every single user can login his own jupyterlab, but the original kernel (python3) for jupyterlab does not have additional packages or dependencies so user must install by himself.
I want to import some packages in the kernel before hub is published, how to do that ?
You should be able to build your own Docker images using your existing image as a base. You could also look at e.g. Jupyter Docker Stacks — Docker Stacks documentation as a base.
What have you tried so far?