Abstract: In order to realize the environment friendly and high efficient water drive development of off shore oil field and meet the demand of deep fluid flow diversion technology，the research on the performance and influencing factors of the environment friendly inorganic precipitating diversion agent was developed. Results showed that the sodium silicate solution reacted spon taneously with the Ca2+ and Mg2+ of injected water in the high salinity block of Bohai oilfield，and the precipitated suspension from the reaction played a role of liquid flow diversion. Considering the factors of precipitation amount，cost of the agent and injection technology of mine area，the physical model experiment was carried out by alternating injection under the recommen ded concentration of 0.02~0.05 mol/L.The experimental results showed that the plugging effect increased with the increase of permeability.With the increase of concentration of Ca2+，Mg2+ and sodium silicate，the amount of precipitates increased，and effects of plugging and profile control were improved.Microscopic visualization experiments showed that the system reacted once in contact with the pores of the reservoir，formed precipitates，reduced the cross section of pore flow，increased the filtra tional resistance，the injection pressure and the pressure differences between the medium low permeability zones，thus increa sed the amount of liquid absorption，reached the goal of deep fluid flow diversion and expanded sweep efficiency.This techno logy has great application and popularization value in off hore and other high salinity oil fields with limited working space.

Key words: offshore oilfield；inorganic precipitating diversion agent；deep fluid flow diversion；microscopic visualization； mechanism analysis.