The formation of ecosystem services depends on ecological processes at a certain spatial and temporal scale. Therefore, exploring the characteristics, correlations, and effects of ecosystem services in different spatial scales has importantly theoretical value and practical significance for enriching the sustainable management of ecosystem services. Taking Ansai District, a typical grain for green county, as the study area, the spatiotemporal changes of six ecosystem services were quantitatively evaluated based on ecological models. The correlation coefficient method, bivariate spatial autocorrelation, and geological detectors were used to reveal the scale effects and differentiation mechanisms of ecosystem service relationships at different spatial scales. The results show that: (1) the ecosystem services are mainly synergetic in the retired farmland area, among which the synergetic relationship between regulatory services and support services is the strongest (|r|≥0.5), while the trade-off relationship occurs between cultural services and other services. From the time series perspective, the relationship between regulatory services and support services is relatively stable, maintaining a synergistic relationship during the research period, and the degree of synergy has improved after returning farmland to forests. (2) The spatial scale characteristics of the relationship between ecosystem services are mainly manifested in the directionality and significance of the relationship. At the grid scale, the interaction relationship between ecosystem services is relatively stable, and the change in direction of action mainly occurs between the grid scale and administrative units. As the research scale increases, the spatial significance of the interaction relationship between services gradually decreases. (3) The trade-off and synergy of ecosystem services are the result of the combined action of natural and social factors. The disturbance of human activities in the abandoned farmland area is relatively small, and the explanatory power of natural factors (q=0.1507) is higher than that of social factors (q= 0.0148). Moreover, the key factors that affect a certain type of ecosystem services play an important role in the relationship between ecosystem services. Among them, the combined effect of land use degree and topographic factors is the main concern of ecosystem service management.