Research on the supply and demand of ecosystem services is still in its early stages, and a set of supply and demand evaluation methods that have region-wide suitability and low data requirements is urgently needed. Given this situation, the present study took prefecture-level cities in Guangdong Province as research units, estimated the ecosystem service demand based on the consumption or desired amount of ecosystem services and calculated the ecosystem service supply based on the value of ecosystem services per unit land area. A method to recognize the regional balance between the supply and demand of ecosystem services based on the Gini coefficient was further proposed. The results showed that the water conservation service in Guangdong had a Gini coefficient of 0.135, suggesting a relatively even spatial distribution; the food production, material production, and soil maintenance ecosystem services had Gini coefficients between 0.293 and 0.423, indicating that their distributions were spatially uneven to some extent but reasonable; the atmosphere regulation and waste disposal services had Gini coefficients above 0.6, representing spatial polarity between supply and demand. The ecosystem service synthetical supply-demand coefficients of Guangdong Province was 0.332 and the cities can be classified according to their equilibrium states of supply and demand into 3 categories: low supply-high demand, relative balance between supply and demand, and high supply-low demand. Low supply-high demand cities can make full use of economic and technological advantages to change the condition of having less supply and greater demand for ecosystem services and reduce ecological risks; cities in which there is a relative balance between supply and demand can improve targeted protection of ecosystem service supplies and pay close attention to changes in supply and demand; and high supply-low demand cities can increase their demand for ecosystem services appropriately on the premise of ensuring ecological security, so as to effectively utilize the supply of ecosystem services. This study provides decision-making guidance for promoting the sustainable development of cities in Guangdong Province and other regions, and for accelerating the development of ecological civilizations.