Straw incorporation is an important agronomic practice for sustainable cropland management, improving soil structure and enhancing soil organic carbon (SOC) sequestration. In this study, a systematic review was conducted using the Web of Science (WoS) database, and a random-effects meta-analysis was performed on 63 field experiments in mainland China, including 846 treatment–control comparisons, to evaluate the effects of straw application rate and duration on soil aggregates, aggregate-associated carbon, and SOC. Across all studies, pooled effect sizes indicated that straw incorporation significantly increased Mean Weight Diameter (MWD) (22%), macroaggregate content (17%), and SOC (25%), while enhancing aggregate-associated carbon in macroaggregates (35%), microaggregates (30%), and silt–clay fractions (22%). It also reduced silt–clay fraction content by 17%, indicating improved aggregate redistribution. Interaction analysis suggested that short-term incorporation (<5 years) at 5–8 t ha⁻¹ and long-term incorporation (≥5 years) at 10–15 t ha⁻¹ were more favorable for macroaggregate formation and carbon sequestration. Precipitation negatively affected microaggregate carbon, highlighting environmental regulation of carbon stability. Overall, straw incorporation strengthens soil structural stability, promotes SOC accumulation, and provides evidence-based guidance for sustainable residue management and climate-smart agriculture in mainland China.