This study aimed to uncover montane biodiversity and relations with the surrounding vegetation.Based on plot survey,floristic spectrum,diversity index,correlation and cluster analysis,plant floristic diversity of Laotudingzi were analyzed.The results showed that:(1)The occurrence of 1 006 wild seed plant species demonstrates that Laotudingzi have a high floristic biodiversity.It is notable in dominant family,the single-species and few-species genera of angiosperm are rich and it shows some relict phenomenon.(2)The distribution types of species are various and complex.The flora is ancient and it has not obvious phenomenon of endemic genera and species.The dominance of temperate elements is obvious,it fits North China flora from warm temperate.(3)Compared with adjacent mountains,floristic Shannon-Wiener index are obviously different from other 9 moutains,while simpson index are not.Shannon-Wiener index of Lushan and Culaishan are quite high,while Baishilazi and Changbaishan are low.(4)According to the relativity of different mountains flora,10 moutains correlation is significant at the 0.01 level,and the coefficients are between 0.617 and 0.995.Greater similarity was found among Laotudingzi,Qianshan and Fenghuangshan by cluster analysis,and they are all classified as North China flora.The present date indicated Laotudingzi should belong to subarea of North China montane flora.