You should put the checktime date in the where clause of the sub query in order to check for non existence of employees on that date.
Assuming the checktime is of datetime type, try this:
DECLARE @attendance_date datetime
set @attendance_date = '2014-02-20'
select TM.TM_UserId, TM.FullName, @attendance_date from TM_User TM left join Employee_Attendance EM
where TM.Is_Active=1 AND NOT EXISTS
(SELECT * from Employee_Attendance EM2 WHERE EM2.CheckTime=@attendance_date AND
EM2.EmployeeID = TM.TM_UserID )