Corruption is the activity where public servants abandon their duties and disobey the law, and collaborate with others in taking the economic rent out of the state. The corruption function model shows that the state controls the economy and creates economic rent, which is the fundamental source of corruption. The more the rent is, the more the corruption is. And the discretionary powers of public officials increase the frequency and magnitude of corruption, whereas their accountability has the opposite effects. The law and discipline punishment might suppress corruption but could not wipe it out. Corruption could co-exist with the fast growing stages of economic development, which forms a kind of paradox. Corruptions shock those "evil laws" during the fast-growing and transformation periods, and tend to help improve the economic efficiency.