The invention provides a construction method of steel pipe and glass fiber reinforced plastic mortar pipe connection. The construction method comprises the steps of manufacturing a steel socket pipe (2) and a steel variable diameter pipe (3) capable of sleeving the end of a glass fiber reinforced plastic mortar pipe (1); sleeving one end of the glass fiber reinforced plastic mortar pipe with a rubber ring (5); pulling the steel socket pipe outside the end, sleeved with the rubber ring, of the glass fiber reinforced plastic mortar pipe; welding the outer end of the steel socket pipe and the large opening end of the variable diameter steel pipe; using a round ring plate (6) to seal the end in the steel socket pipe and perforating the steel socket pipe to pour high-strength shrinkage-free pouring slurry, and meanwhile, using glass fiber cloth (7) in combination with resin to twine an outer opening of the junction of the steel socket pipe and the round ring plate; welding a water drainagepipe (8) to the bottom of a steel pipe (4) and then welding the small opening end of the variable diameter steel pipe with the steel pipe (4). The technical problem of the steel pipe and glass fiber reinforced plastic mortar pipe connection is effectively solved, the construction efficiency is improved, and the engineering quality is guaranteed.