Abstract: The setting time of geopolymer foam concrete (GFC) does not match with the construction demand, and the pressure resistance is too high in the case of high volume weight, which is not conducive to the subsequent excavation and maintenance. Based on the performance requirements of backfill, the effects of gypsum content, sodium silicate content and precursor ratio on the fluidity, setting time and compressive strength of GFC were revealed using single factor test. A composite excited high volume weight foamed concrete for underwater pipeline filling was proposed by X-ray diffraction (XRD) for the study of GFC hydration products. The test results indicate that the fluidity and compressive strength of GFC can be significantly improved with the increase of sodium silicate content, the setting time rises first and then falls, and the compressive strength increases first and then decreases with increasing gypsum content. The gypsum excited GFC provides strength in the early formed ettringite, which produces an amorphous C-S-H gel when mixed with sodium silicate. The composite excited polymer foam concrete with high bulk density prepared in this paper provides a new idea for backfilling protection of underwater oil and gas pipelines.