Alibaba Group is one of the most active companies involved in open source in China. Why Alibaba actively embrace open source? what open source projects we have been participating? and what we gain in open source development? This talk will give a brief introduction about Alibaba Group, will take Taobao.com as an example for building software infrastructure based on open source software and home grown software, where picture storage system, CDN system and database system will be presented to see how the systems were evolved from commercial products at the beginning, and will conclude some experience during this process. Then, it will list major open source projects that Alibaba have started and been involved, and will share open source procedure in the company. Finally, it will discuss the benefits of open source development from both developer perspective and company perspective, and conclude the reasons of embracing open source.