The demand for the ride-hailing platform under the concept of “sharing economy” has the characteristics of random occurrence and fluctuation. For pricing problems of the ride-hailing platform with different conditions of supply and demand caused by the demand fluctuation, using the optimal control theory, the platform dynamic pricing model under the supply capacity in which the object is to maximize platform expected profit is constructed. The optimal dynamic price solution is deducted using the Pontryagin maximum principle, and the demand rate and supply rate are presented. Results show that the optimal price of the ride-hailing platform dynamically adjusts the ride supply and varied with the ride demand fluctuations. Especially, the delay of demand orders will be reduced significantly through the optimal dynamic price in peak demand. Finally, numerical experiments are conducted to verify the model and to further explore the influence of service quality of platform and variation coefficient of market demand on optimal price and expected revenue.