In my development environment, log file can be correctly created, but when I release my project(.net) to IIS web site and run my project, log file haven't been created!
You sure that the proper write/create permissions were given on the webserver where the log file was suppose to be created? That could be the potential reason. Make sure that the proper security permissions are given.
I haven't install the enterprise library on the IIS server. It is not necessary, right?
Right, it is not necessary.
Have a look at the details here: Logging Application Block
In case needed, a sample implementation here: Get Logging with the Enterprise Library