The invention relates to a multi-functional bridge seamless expansion device and a construction technology. The multi-functional bridge seamless expansion device comprises an expansion system, a supporting system, a car stopping system, a detecting and data collecting system, an analysis system, an alert and display system, a wifi and GPS system and a controlling system. The construction technology comprises the steps of cutting, sliding groove forming, stand column and sliding column installing, radar antenna installing, stress and strain detector installing, amplitude and frequency detector installing, car stopping system installing, expansion system installing, sound broadcaster and displayer installing, control switch installing, wifi and GPS system installing and analysis system and alert system installing. The multi-functional bridge seamless expansion device and the construction technology have the advantages that universality is high, the service life is long, the cost is low, the construction speed is high, maintenance is convenient, the maintaining cost is low and traffic open is fast.