Highpressure steam injection method is the major method of exploitation of heavy oil reservoir. In steam injection pipe network, the fluid in steam, liquid and solid phases scoured the bend and led to leakage. Based on the turbulence models, multiphase flow models, discrete phase models and erosion models ,and considering the mutual coupling of the different phases, the numerical simulation of the flow of the three phases in the bend flow was established. The results show that in the steam injection pipelines，as bending degree of the bent pipe increased， the distribution and wall wear area of the liquid phases and particle phases moved backwards step by step，and the value increased accordingly. Moreover, the increase of liquidphase volume fraction in the pipe wall could effectively reduce the surface corrosion of the solid phase.

Factors that affect pipeline safety and reliability are numerous and randomness, so directly solving the limit state equation is difficult. The solving process of using RF method is simple and high precision. Based on reliability theory and B31G-1991 standard, comprehensively considering the randomness of the corrosion defect length, radial depth of defect, the corrosion rate, wall thickness, pipe yield strength and pressure pipelines, using RF method established a mathematical model for the reliability analysis of corrosion piping. The computer program for this method was developed. The results show that reliability index of the pipe decreased with the increase of defect length, defect depth, and the radial in corrosion rate and that the defect depth is the main factor of pipeline failure. The pipeline reliability index with the pipe yield strength increases in a linear increased, and rapidly reduces with inside pressure increasing.