Abstract: Zhongba archaeological site(30°20'43″N,108°01'37″E,elevation 135~148m)is located in the terrace of Ganjing River,6km from Zhongxian County,Congqing City.Archaeological evidence from the Zhongba site indicates that salt production was well developed in a time period more than 4000a B.P old.To explore the natural background of the salt production and its effect on the environment,samples from a cultural layer with a depth of 12.5m in Zhongba archaeological site were collected for pollen analysis.According to AMS14 C dating data,these samples were divided into three groups: late Neolithic period(4420~3700aB.P.),Shang & Zhou Dynasty(3550~2700aB.P.)and Eastern Zhou Dynasty(2700~2300aB.P.).Pollen analysis shows that the herb pollen and fern spores including Poaceae,Elatostema and Athyrium are dominant taxa in all of the samples.Tree and shrub pollen of Pinus,Betula,Pterocarya,Quercus and some subtropical species including Apocynaceae,Ligustrum,Loropetalum,Liquidambar,have relatively low percentage values.Intensive human activities,mainly deforestation and salt production,have been existing in the Zhongba archaeological site and the vicinity since the late Neolithic.Shrub,grassland and cropland were,therefore,widely distributed.Forest was destroyed to form shrub and grassland near the Zhongba archaeological site during the Neolithic period(2700~2300aB.P.).Human impact was still strong during the Shang & Zhou Dynasty(3550~2700aB.P.)although the climate became dry,implying that climate change had little effect on the salt production.The climate became warmer and moister during Eastern Zhou Dynasty(2700~2300aB.P.),in the meantime the scale of salt production and farming expanded,which resulted in widespread deforestation and promoted grassland development.