Low salinity water flooding means injecting water with salinity of 1—5 g/L into the formation to enhance oil recovery. The mechanism of low salinity water flooding to enhance oil recovery is still controversial. By sorting out the development history of low salinity water flooding technology，the main mechanism of enhanced oil recovery by low salinity water flooding in sandstone reservoir could be roughly divided into two aspects，such as particle migration and wettability change. The mechanism of enhanced oil recovery by low salinity water flooding in carbonate reservoir was briefly described，including the change of double electric layer and ion reaction caused by mineral dissolution. The reservoir condition suitable for low salinity water flooding technology was analyzed. Then the new technology combining low salinity water flooding with other oil flooding technology was summarized. The application of molecular simulation technology in low salinity water flooding was introduced. Finally，some suggestions for future development were put forward.