The invention provides a detecting and warning device for shaft breakage faults of chain belts of a pig casting machine. The technical scheme includes that the detecting and warning device comprises pig casting dies and chain belt strips; the chain belt strips are supported by chain belt rolling support shafts, the chain belts on the chain belt strips are connected with one another by chain belt connecting shafts, the corresponding chain belt connecting shafts on each two chain belt strips are connected with each other by a connecting rod, warning devices are arranged on the side surfaces of the chain belt strips and comprise touch switches and touch extension arms, the touch extension arms drive the touch switches to be closed, the touch switches are connected with a PLC (programmable logic controller), the PLC is connected with a display screen, each touch switch is further serially connected with an alarm, each speed encoder is connected with the PLC and is connected with the corresponding chain belt rolling support shaft, and the speed encoders and the chain belt rolling support shafts can rotate coaxially. According to the scheme, the detecting and warning device has the advantages that warning effects can be realized by the aid of the touch extension arms, the touch switches and the like under the conditions such as breakage, deformation and falling of the chain belt connecting shafts, and accordingly the safety of equipment, personnel and production can be guaranteed.