The invention discloses a parking space reservation and allocation method and system based on dynamic optimization. The method comprises the following steps: S1) dividing a geographical range covered by network reservation and allocation parking service into a plurality of parking areas, establishing a data structure table and loading a basic data and initializing a time window; S2) opening the time window, collecting parking space supply and demand information of each parking region, and judging parking space supply and demand conditions of each parking region; S3) carrying out reservation and allocation on parking spaces in each parking area through a dynamic optimization method based on the principle of enabling parking space total use ratio to be maximum and the principle of enabling parking space available time fragmentization to be minimum to obtain an allocation result; and S4) sending the allocation result to a parking space demander terminal, a parking space provider terminal and a parking space intelligent management system. The method and system can improve parking space use ratio from multiple angles, thereby reducing parking space resource waste and relieving the problem of hard parking in cities.