ABSTRACT Improving farmland yield is one of the most critical options for increasing grain production and ensuring food security worldwide. The High‐Standard Farmland (HSF) project is China's largest investment in farmland infrastructure, designed to enhance grain productivity, promote rural equity, and close regional yield gaps by improving farmland quality and resilience to environmental stress. However, the HSF project's effects on national‐scale productivity trends and spatial heterogeneity remain poorly characterized. Here, we analyzed spatiotemporal changes in the farmland productivity in the 2330 HSF project areas using time‐series remote sensing images and the Vegetation Photosynthesis Model and evaluated the effectiveness of HSF projects on productivity enhancement. We found that 92% of the HSF project areas experienced farmland productivity improvement, and 38% of the HSF project areas experienced an average annual farmland productivity increase of more than 1500 kg/ha (the target threshold in the HSF projects). Spatially, productivity improvements in HSF project areas were predominantly concentrated in North China, while South China showed no significant gains. At the provincial scale, the more HSF project regions were implemented, the higher the rate of increase in farmland productivity. Previous studies found that the HSF projects improved low‐ and medium‐yield farmland productivity, while we found that high‐yield farmland had higher productivity improvement than low‐ and medium‐yield farmland, suggesting high‐yield farmland was more efficient for enhancing yield and grain production. For future HSF projects in China, we proposed three distinct project area types, each requiring region‐specific implementation strategies based on local agricultural conditions. This study can provide guidance for future strategies to increase farmland yield and grain production.