The invention provides a multi-occasional application waste gas purifying device for environmental protection engineering. The waste gas purifying device comprises a moving tray, moving roller wheels,a traction rod, a purifying tank, an exhaust chimney tube, a conveniently-connected adjustable gas inlet bellows structure, an electrostatic waste gas dust-removing box structure, a circulatable waste gas neutralizing and spraying tank structure, a waste gas purifying barrel structure, a flow-guiding partition board structure, a waste liquid recycling tank, a main partition board, a traction hole, a suction connection control switch, an electrostatic dust removal control switch, a spraying circulation control switch, an exhaust control switch, an exhaust fan and a protective hood. Through thearrangement of a waste gas inlet bellows, a first connecting flange plate, a second connecting flange plate, a gas inlet hood, a first connecting lug plate, an angle adjusting hydraulic cylinder anda second connecting lug plate, rotating adjustment of the second connecting flange plate through the angle adjusting hydraulic cylinder according to different using occasions is facilitated, and connection with a waste gas emitting port is facilitated.