Abstract: Tree Sparrows (Passer montanus) used to be a dominant bird widely distribution in Sichuan Province.It was found that they had disappeared twenty years ago in the farming region,city and town of Sichuan basin,mountainous area around basin and southwest of Sichuan,and this phenomenon continues up to now.Investigation results (Jul.,1995-Oct.,2000) and historical data reveal that the disappearance of Tree Sparrows began in Sichuan basin at the end of the seventies or the beginning of the eighties;in the eighties,it expanded from the basin to mountainous area around basin and southwest of Sichuan ;in the nineties,the distribution pattern had taken shape into the rare,the partial and the extensive distribution region.The discussion indicates that the causing disappearance and geographic distribution change of the Tree Sparrow in S ichuan is a result of abusing Organic Phosphoric Pesticide.