Based on the pollen analyses of Niya section which is located at southern margin of the Tarim Basin, this paper probes into the paleoenvironmental evolution during historical times （since about 4 000 a BP） in this district. The paleoenvironmental information stored in pollen assemblage coincides with that revealed by other geological indices, such as the ratio of geo chemical element, low frequency susceptibility and δ¹³C. The results show three relative humid periodes has been identified, i.e., about 3 600 a BP （1 650 BC）, 2 500～1 900 a BP （550 BC～50 AD） and 1 400～1 000 a BP （550～950 AD）, although the macro background of drought consecutively existed. This paper also reflects that （1） studies of pollen assemblage of arid area provide useful information on paleoenvironmental changes; （2） the two abnormal high values of Gramineae appeared at 1 70～1 60 m （100 BC～50 AD） in this section imply intensified human agricultural activities during this period; （3） what's more interesting is this period incarnates apparent relative humidity reflected by pollen data and other indices.