Abstract: This paper examines the two-phase flow for a horizontal well penetrating anaturally fractured reservoir with edge water injection by means of a.fixed streamlinemodel. The mathematical model of the vertical two-dimensional flow or oil-water for ahorizontal well in a medium with double-porosity is established, and whose accuratesolutions are obtained by using the characteristic method. The saturation distributionsin the fractured system and the matrix system as well as the formula of the time ofwater free production are presented. All these results provide a theoretical basis and acomputing method for oil displacement by edge water from naturally fractured reservoirs.