The dynamic pricing model of the perishable product with the price-dependent demand using the optimal control theory is established．
The objective is to maximize the total sales profit within the sale planning horizon． The optimal conditions of the sale price are
obtained according to the Pontryagin maximum principle． And if the sale price is between the unit purchasing cost of the product and the
upper limit of the sale price，a lower limit of the optimal sale price and a higher limit of the optimal inventory level at every time point
of the sale planning horizon are obtained which are both related to the perishable rate and the unit holding cost of the product at every
time point of the sale planning horizon．