kiran2401 says:
set @aa='insert into Employee(EMPID,EMPNAME,EMPLname) select '+@EMPID+','+@EmpName+','+@EmpLname+ ' from Employee'
Please replace above code with
set @aa='insert into Employee(EMPID,EMPNAME,EMPLname) select '+ CONVERT(VARCHAR(50),@EMPID) +','+@EmpName+','+@EmpLname+ ' from Employee'