How can i check How many user is connected to my Domain Controller ? and user list ?

Users do not remain connected to domain controllers, they authenticate and the domain controller does not 'hold' a connection.  If you want how many authenticated, look in the security log to find the events related to authentication.

But if you want how many users are in AD then you can use PowerShell

• Proposed as answer by Mary DongMicrosoft contingent staff, Moderator 5 hours 38 minutes ago

You have to enable auditing and then check the event logs for account logon in the specific time frame. Or you use monitoring software like SCOM. http://technet.microsoft.com/en-us/library/cc731607(v=ws.10).aspx

Alternatively, you may try using Lepide last logon reporter tool that is available free and might helps you obtaining such reports.