Under low and suitable phosphorus, 545 accessions of the core collection of Yunnan rice landraces were studied for the heading date. The results showed that there was comparatively significant difference between the different degrees of stress for low phosphorus. The heading date of most rice accessions under low phosphorus condition was later than that under suitable phosphorus condition. (2) There was great difference in the heading date of rice core collection in different rice cropping regions or prefectures because of the long history of adaptetion . (3) Among 5 rice cropping region except the northwest cold japonica region, the difference of their heading date was extremely significant. Under two stress conditions mentioned above, but there were difference only in five prefectures under low phosphorus condition.