What did he do as a leader of China?

Qin Shi Huang brought China under a unitary system of government. By doing so, it had created a sense of unity amongst the people. He standardized the currency, measurements and Chinese writings. He controlled all of the lands which were still under the power of feudal Shi. With 36 provinces divided, each is under the direct control of Qin Shi Huang. This system of government continued for the next 2200 years.