ing at the slow development of rice mechanical transplanting in the Yangtze River Valley, we explored the effects of mechanical transplanting densities and nitrogen application on yield formation and nitrogen use efficiency (NRE) in a field experiment with the conventional variety Zhongjiazao17 as material. The results showed that the grain yield didn’t significantly increase with the increasing levels of transplanting density. At the high density (36.4 hill /m²) and high nitrogen rates (175.5 kg/hm² in early season, 189 kg/hm² in late season) the grain yield maximized, being 7.84 t/hm² in early season and 9.10 t/hm² in late season, while the difference was not significant comparied with high transplanting density plus medium nitrogen rate (110 kg/hm² in early season, 140 kg/hm² in late season). Meanwhile, the interaction between the density and N application was not significant. NRE declined as the N application level increased, while it improved as the density increased. N recovery efficiency at the medium N level was 13.26% higher on the average compared with the high N level. And N recovery efficiency at the high density increased by 17.53% compared with the low density. As a result, at high transplanting density and low nitrogen application level, high yield was achieved by increasing effective panicle number per unit area, and N recovery efficienly was improved. It is a key technology for the high-efficiency and high-yielding cultivation of mechanical-transplanted rice in the Yangtze River Valley.