The 3rd Electricity reform in UK has been implemented which includes capacity markets. Among many parts of capacity market, the demand side is the key part for government imposing their force on promoting the market into the planned direction which is to meet the reliability standard. This paper gives a brief overview on demand side of capacity markets in different countries, and compares creatively their similarities and differences from the combination of reliability and market perspective. The main similarities are the core of capacity market and the force of government. And the differences focus on the capacity mode, capacity requirement and the length of capacity agreement. Finally, combined with the new electricity reform in China, this paper gives some suggestions in demand side for the future creation of capacity market in China according to the results from comparisons.