Steel rail number spray-marking device taking rail measurement trolley as carrier

The invention discloses a steel rail number spray-marking device taking a rail measurement trolley as a carrier. The steel rail number spray-marking device comprises the rail measurement trolley and a spray-marking machine; the spray-marking device comprises a base plate, a guide shaft, a flexural beam and a spray-marking head, wherein front and rear shaft bases of the guide shaft are supported on the base plate; the flexural beam is fixedly arranged at the guide shaft; the spray-marking head is fixedly arranged at the bottom end of the flexural beam; the guide shaft is provided with a protection mechanism which is used for protecting the spray-marking head from obstacles; the protection mechanism is composed of two annular grooves, an axial through groove, a stop pin, a central blind hole, a central spindle, an anti-rotation mechanism and a planar volute spiral spring, wherein the axial through groove communicates with the two annular grooves; the stop pin is jointed with the axial through groove; the centra