The invention provides a wheel rail acting force and tread failure detecting system and method. The system comprises a triggering unit, n measuring units and a system control and data processing unitconnected through circuits; n is a positive integer, and is an even number larger than 2; the triggering unit generates triggering signals when trains pass by, and sends the triggering signals to thesystem control and data processing unit; the n measuring units emit laser for collimation, transmission and reflection to obtain light spot position electric signals after receiving the signals of thesystem control and data processing unit, and return the light spot position electric signals to the system control and data processing unit; and the system control and data processing unit receives the triggering units of the triggering unit to trigger the measuring units, and receives the light spot position electric signals of the measuring units to obtain wheel rail acting force and tread failure detecting results. The system can quantitatively detect multiple tread failures to realize synchronous and quick detection of wheel pair and steel rail acting force and tread failures.