Selenium, an essential micronutrient for humans, plays a pivotal role in maintaining normal physiological functions, including antioxidation, cardiovascular protection, immune enhancement, and cancer prevention. Given the widespread selenium deficiency in 72% of China's soil, converting inorganic selenium to organic selenium through crop application represents a safe and cost-effective supplementation approach. This study systematically evaluated the effects of selenium application on yield and quality improvement in rice, wheat, and maize to provide a theoretical basis for scientific selenium fertilization. A total of 134 field trial studies (2013-2024) from CNKI, VIP, Wanfang, Web of Science, and PubMed databases were included, using keywords like "selenium", "wheat/maize/rice", and "yield". The natural logarithm of the response ratio (lnR) was employed as the effect size for Meta-analysis, with data processed using Microsoft Office, Get Data Graph Digitizer, and MetaWin 2.1. Overall, selenium application increased the yield of rice, wheat, and maize by 5.41% (95% CI: 4.74%-6.08%, P_Q<0.01). Notably, wheat and rice yields increased significantly by 8.72% (95% CI: 7.69%-9.75%) and 6.35% (95% CI: 6.34%-7.71%), respectively, while maize yield showed a negligible increase of 0.46%. Selenium application remarkably elevated grain selenium content by 164.09% (95% CI: 156.15%-169.21%, P_Q<0.01), with maize demonstrating the most pronounced effect (172.97%, 95% CI: 164.55%-181.39%). The quality improvement of grain starch content was 2.39% (95% CI: 1.71%-3.06%, P_Q<0.05), significant only in maize (3.87%, 95% CI: 2.86%-4.88%). A positive but non-significant effect was observed on grain protein content (4.99%, 95% CI: 3.78%-6.20%), with maize showing the highest enhancement (8.90%, 95% CI: 4.45%-9.17%). Effects varied significantly by crop type, application method (foliar spraying outperforming soil application), region (East China showing the strongest response), and soil selenium content (rice/wheat optimal in moderate selenium soils, maize in low selenium soils). Selenium application proves effective for yield and quality improvement, but strategies must be optimized based on crop, regional, and soil conditions to ensure human selenium nutrition and agricultural productivity.