Mechanically transplanted rice has many advantages, such as stable yield, high efficiency, saving cost and freeing labor, and the area of mechanically transplanted double-rice has been larger and larger in China in recent years.However, the combination of agricultural machinery with its supporting agronomy technology, such as the optimal basic population and the rule of tillers, still needs to be further studied.In order to accurately determine planting density and make reasonable use of tillers for mechanically transplanted late rice, we examined the characteristics of tillering and panicle formation and the parameters related to basic population formulae using the combination of 3 high-yield late rice (Hyou 518, Hyou 159 and Wuyou 308) as study material.The 3 experimental materials were grown in the field of Shanggao, Jiangxi Province, China in 2013 and 2014.And the experiment was conducted under the condition of mechanically seeding and transplanting with high-yield agronomy technology during the whole growth period of late rice, and 3 replicates were for each treatment.Using the method of the tillering tracking, 10 holes of seedlings were set in each replicate to investigate the leaves and tillers emerging, panicles formation, and panicles traits on different nodes of each stem.The results showed that the primary tillers of the mechanically transplanted late rice were initiated mainly from the leaf positions of 3~7 on main stems, and the leaf positions of 3, 4, 5 and 6 was the superior positions for tiller initiation and panicle formation.The secondary tillers emerged from 3/0 to 5/0, such as 1/3, 2/3, 3/3, 1/4, 2/4 and 1/5, but panicles were formed mainly in 1/3 and 1/4.The panicle formation was mainly from the primary tillers, and the secondary tillers could form a few panicles.The panicle number per plant was about 4.5 for late hybrid rice in mechanically transplanting.Panicles on both main stems and tillers of superior leaf positions showed better properties and higher productivity, thus making greater contributions to the group yield.Appropriate number of panicles per stem, especially the panicle number of tillers of superior leaf positions is the premise of high-yield cultivation, which particularly increases the grain yield, not only for the panicle number, the branch number, the grain number, the setting percentage, the grain weight, and the spike weight, but also for more harmonious yield factors.For late hybrid rice mechanically transplanted at the stage with 4~5 leaves, the leaf age without tillering was 0.7~0.8, with the adjusting factor of 0.6 and the effective tillering rate of 0.8.In conclusion, in order to obtain a high yield of mechanically transplanted late rice, the key strategy is to ensure a reasonable number of basic seedlings, and then promote tillering as early and as much as possible, by increasing the effective tillering rate.The experiment indicates the rules of tillers emergence and panicles formation for late rice in mechanically transplanting, which provides a theoretical reference for the accurate density of planting and efficient utilization of the farm equipment in field production.According to the tilling characteristics of late rice transplanted by machine, the optimal management measures of seedling, manure, water and planting density should be further studied for giving full play to the middle tillers(tillers of superior leaf positions) of main stems.In addition, this study just includes the experimental datum of 2 years in the same late rice field, and further studies about the validation and perfection of multiple years and sites should be considered.