This study examines the spatiotemporal evolution, regional disparities, state transitions, and driving factors of pesticide use intensity in China’s grain crops from 2005 to 2023. Using provincial panel data, pesticide use in grain crops was estimated by an area-proportional allocation method, and pesticide use intensity was measured as pesticide input per unit of grain output. Using agricultural new-quality productive forces (NQP) as a regional stratification framework, provinces were grouped into low-, medium-, and high-level regions. Kernel density estimation, GE0 decomposition, Markov chain analysis, and LMDI decomposition were employed to investigate distributional evolution, disparity sources, transition characteristics, and driving mechanisms. The results show that pesticide use intensity declined in all three regional types, with the low-, medium-, and high-level regions decreasing from 1.71, 1.77, and 2.75 kg/t in 2005 to 1.16, 1.07, and 1.72 kg/t in 2023, respectively; the high-level region recorded the largest reduction (1.03 kg/t). Kernel density curves generally shifted leftward and became more concentrated, indicating an overall decline and partial convergence, although a persistent right tail suggests that some high-intensity provinces remained. The GE0 index rose from 0.216 in 2005 to a peak of 0.283 in 2013 and then declined to 0.248 in 2023, while intra-regional disparities consistently dominated overall inequality, accounting for 86.1% in 2005 and 88.7% in 2023. Markov results show strong state persistence, with no direct transitions between low- and high-intensity states. LMDI results indicate that the sharpest decline occurred during 2016-2020, mainly driven by the negative shift in the total pesticide use effect, while grain output continued to exert a downward influence. These findings suggest that pesticide reduction in China’s grain sector is characterized by gradual adjustment, strong within-group heterogeneity, and differentiated regional pathways and therefore requires more targeted governance strategies that balance food security with green agricultural development.