I have given some amout to our office staff as a loan. He will be back it after some days or some months . So how can write that transaction ? What is the rules about this transaction.

Assuming he's really planning on paying it back, it's just a receivable. You may want to put it in a separate receivable account than your customers. "Employee receivable" or some such. If you have reasonable expectations that it will get paid within the one year limit of current assets, then make it current.