Question

How did Shi Huangdi support a unified China?

Answer 1

Shi Huangdi also known as Gin Shi Haung, had made the whole country use the same currency. One example that he did was build the Great Wall of China. He also ended the feudal state system. 

Answer 2

he unified tons of stuff :3
coins (currency), language (written), and built now roads. he also unified some of the types of measurements used in the country.