The invention relates to a dangerous and old house monitoring system. For main features of settlement and cracks and the like of dangerous and old houses, corresponding terminal monitoring instruments are designed to carry out long-term uninterrupted monitoring on key positions and dangerous points of the dangerous and old houses to obtain reliable and accurate long-term dynamic monitoring data; signals of the terminal monitoring instruments are gathered and processed through a control center to realize real-time evaluation of the current situation of a target object; the signals are transmitted to a background server through GPRS/3G/GSM communication technology; and a management platform computer can randomly observe dynamic change of specific building settlement and wall cracks and transient radical changes before collapse, thereby providing assistant basis for house danger-relieving work decision, and issuing early-warning reminding in time when abnormity occurs.