my supervisor ask me to prepare a polciy regading handover policy which mean when somebody take a vacation he/she must submitt his/her duties and responsiblities to another employee.
could you please help me.
The key to this is to have tasks and procedures documented in advance. In my experience, the more an employee wants to resist documenting tasks and processes, the more I want to know why they don't want to do that. It sometimes turns out poorly but sometimes people just don't have any time.
The smaller the company, the harder this is because people are probably already tightly staffed.
If you have your positions' tasks and methods for obtaining goals and their administrative means for interacting with other persons or departments, it should be relatively easy. If your company has never taken that step, trying to bandage it little bits at a time when people are on vacation will probably not do much to demystify how your company does what it does and not save you if the person on vacation gets eaten by a pteradactyl while they are away.