Abstract: This paper studies the micro mechanism of sharing economy between cities from the perspective of new classical economics.The results show that:(1)the sharing economy between cities comes from economies of specialization of the individual in the production of the products in the other cities,and increases with the improvement of The degree of economies of specialization;(2)The emergence of sharing economy between cities requires the division of labor between cities,and the formation of inter-city division of labor requires that the inter-city transaction cost coefficient be reduced to a certain threshold;(3)The increase of sharing economy between cities can make the inter-city transaction cost coefficient required by inter-city division of labor bigger.