Abstract: Field experiments and the nationwide multi-sites experiments were carried out to investigate the effects of chlormequat-uniconazole 300 micro-emulsion (ME) on improving the lodging resistance and the yield of rice.Spraying at the early jointing stage of rice,the results showed that the gibberellin (GAs) content in internode,the basic internode and the diameter of the internode were significantly reduced,the dry internode weight was increased,the lodging resistance was improved,the grains/panicle were increased from 8.3% to 10.5%,the unripe grain ratio of rice was decreased from 3.8% to 12.4%,and the yields were increased from 2.0% to 5.3%.The tests of national multi-sites experiments have the consistent results.