In order to establish high-yielding population of rice and reveal its yield formation rule in the southern Northeast Plain, an experiment with different cultivation densities was conducted, with the main high-yielding rice varieties Liaogeng 401 and Liaogeng 212 in Liaoning Province as test materials. The results showed that the effective panicles number per unit area increased significantly in the high planting density treatment （row spacing 20.0 cm×13.3 cm）, resulting in a higher yield, but the yield difference was not significant with the low planting density treatment （row spacing 30.0 cm×20.0 cm）. Under the low planting density treatment, although the number of effective panicles is small, but the number of grains per panicle increases, so it also has a relatively high yield level. High planting density can build a multi-spike population that relies on increasing the number of tillers and more material accumulation in the population to obtain high yield. While low planting density can build a large-grain population by promoting material transfer and transformation, improving harvest index and forming large panicle and grain to obtain high yield. It can be seen that by balancing the relationship between the effective number of spikes and the number of grains per spike, ensuring the number of spikelets in the population, while ensuring a higher seed setting rate and 1 000-grain weight, a stable and high-yield population can be obtained.