U- Pb datingwas carried out for zircons from top of the tuffaceous sandstone and bottom of tuffaceou volcanic breccia in the Jianchuan Formation. Combined with the age data of the granite veins within the Jianchuan Formation, the study constraints volcanic event within the ages of 36.23±0.88 Ma to 35.46±0.76 Ma, suggesting the Caijiachong stage of Late Eocene in time. A large number of palynomorphs found in the upper part of the section reflects that the margin of the Jianchuan basin was covered by evergreendeciduous broad- leaved mixed forest in this period, which was distinctly characterized by the vertical zonation of vegetation. Combined with elevation, annual average temperature and annual precipitation recorded by the fossils which has closest relation with the palynomorphs, this study obtained the average annual temperature of 13.3- 14.9℃, the average annual precipitation of the range of 863.3- 1344 mm, and the paleoelevation of 1900±100 m for the Jianchuan Basin during Late Eocene using the coexistence analysis of the main palynomorphs. Integrated comparison of paleontological data, oxygen isotope, volcanic event and tectonic thermodata indicates that under the effect of collision of India and Eurasia plates during the Late Eocene, the western area of Yunnan shows the obvious difference in evaluation, with highest up to 2000~2700m and lowest down to 1200 m, even to sea level, accompanied by the formation of a series of pulling basins and volcanic events.