This study explain the fluctuation and instability of China's leasing industry by the theory of in complete contract and evolutionary economics. The result shows that the fluctuation of China's leasing industry is caused by volatility of different parties in the long run. but for the short term .the mess of China's leasing industry is due to the unreasonable competition structure and trading mode. And from the policy perspective. the unified supervision and the introduction of the financial leasing law has become a curtail thing.