Support assembly and construction method of cast-in-place box girder

The invention provides a support assembly and a construction method of a cast-in-place box girder. The support assembly of the cast-in-place box girder comprises a temporary buttress prefabricated base and a temporary buttress, wherein the temporary buttress prefabricated base is a reinforced concrete prefabricated member, and the temporary buttress is fixedly arranged on the temporary buttress prefabricated base. The construction method of the cast-in-place box girder comprises the following steps of: treating a temporary buttress foundation: pre-treating the ground for paving the temporary buttress prefabricated base to be the temporary buttress foundation; setting up the temporary buttress prefabricated base with a reinforced concrete structure on the temporary buttress foundation and pre-pressing and treating on the temporary buttress foundation after the temporary buttress prefabricated base is set up; mounting the temporary buttress on the temporary buttress prefabricated base; and mounting a sequined beret on the temporary buttress. The invention reduces the engineering cost and is beneficial to ensuring the engineering quality.