Why Human resource manager take Passport of employees , when its illegal by UAE law ?

cause most of foriegner workers after company pay alot to get them work and visa inside the country , they start search other company and when he find he leave and the company lose all the cost

Taking the passpot of an employee is a wrong practice. Yes, it is prohibited by law. The HR manager can have the employee's passport temporarily for processing his residence and work permits. When this is done, the HR manager should hand back the passport to the employee. But wait. The HR manager has valid reasons and concerns  that make him keep the passport of the expatriate employee. Having the passport would prevent the employee from leaving the country in case of wrong doings. That way the employee can be held accountable. Moreover, the employer, being the employee's sponsor, is responsible in front of the government, and feels that the best way for him to face this responsibility is to keep the passport in his custody. Am I advocating that the employer should keep the expatriate employee's passport ? Not at all. On the contrary, I firmly believe that the passport should be kept with the employee himself. However, the concerns and motives behind the HR manager's retention of the employee's passport should be addressed by the employer and government as well. The practice of holding the passport of the expatraite employee by the HR manager is not limited to one country, but it is there in many countries as well. We are In the21st century, and this wrnogful practice should be stopped for good. 

I am Egyptian and I do not have knowledge of the laws within the United Arab Emirates

Thanks Hanna Saba  for replying to my question .  Well explained by you about the intentions of HR manager , but its really sad that a jobseeker can't complain to anyone about this practice !