Abstract: Since opening as a commercial port, especially after the World War Ⅱ, Hong Kong has been developing rapidly in social security system. By integrating the changes of Hong Kong's social security system, the paper divides the changes into three parts:embryonic period (before 1970), new development period (1971-1990) and perfecting period (1990-present). Policy and legislation in each period with different economic, social and cultural backgrounds are introduced, which have a positive impact on the maintenance of social harmony and stability.