In order to improve the efficiency of depressurization and injection increase of water injection wells in low permeability reservoirs，the influence of rock surface wettability，interfacial tension and other factors on water injection resistance was studied，on this basis，a multifunctional drag reduction and injection augmenter CNG was developed，the abilities of CNG solution to change oil-water interfacial tension，rock surface electrical property and wettability，and core pressure-lowering and injection-increasing effect were evaluated. The results showed that，CNG could reduce the oil-water interfacial tension to n×10^-3 mN·m^-1（n<10），eliminate core capillary resistance. CNG could also adsorb on rock surface to eliminate negative charge on rock surface and improve the wettability of rock surface to weak water-wet. Therefore，CNG was not only suitable for core depressurization and injection enhancement with residual oil，but also for drag reduction and injection enhancement in strong water-wet reservoirs，and also suitable for pressure reduction，drag reduction and injection enhancement in reservoirs with both residual oil and strong water-wet.For the natural core of a certain block in Shengli oilfield，when CNG was used in the original core without washing oil，the permeability was increased by 48.49% and the displacement pressure difference was reduced by 31.25%；while when CNG was used in the core without residual oil and with water wetting state，the permeability was increased by 36.32% and the displacement pressure difference was reduced by 27.66%.