As gradual increase of Fengcheng heavy oil output in Xinjiang year by year, a part of heavy crude oil is transported to the downstream refinery through the western crude oil pipeline after being diluted. Understanding of physical characters of the mixed crude oil after being diluted is the key link in diluted crude oil pipeline transportation. Domestic and foreign relative literatures are red and analysis is conducted on measured data of heavy crude oil from Fengcheng, diluted oil from Karamay and crude oil from Kazahastan and its mixed crude oil and obtained is the flow property change regularity of heavy crude oil before and after being diluted. Conducted is comparative analysis on measured viscosity data of mixed crude oil and viscosity prediction model calculation results of 17 kinds of mixed crude oils and obtained is the optimum viscosity prediction model suitable for heavy and diluted crude oil from Fengcheng, which can provide viscosity prediction data for western pipeline transportation of heavy crude oil from Fengcheng and provide valuable reference for preparing heavy oil transportation plan.