Abstract: The present paper deals with the process of meiotic divition of pollen mother cells, microsporogenesis and development of male gametophyte of Pinus yunnanensis Franch. It is observed that nonsynchronous phenomenon in meiotic division of PMCs, some development abnormal microspore, chromatid bridge and chromosome segment in anaphase Ⅰ and some cell nuclear division direction is abnormal in male gametophyte development. It is similar with another report that chromosome number is 2n=24 in Pinus yunnanensis Franch.