The invention provides a tumbling risk assessment, a monitoring system and an assessment method on the basis of three nine-shaft motion sensors. According to the tumbling risk assessment, the monitoring system and the assessment method, the tumbling state detecting, the tumbling risk detecting and tumbling protecting device control are achieved. The monitoring system comprises an information collecting module, a wireless communication module and a date analyzing module. The three nine-shaft motion sensors are mainly used, two of the nine-shaft motion sensors are placed in two shoes, and another is placed on the wrest; original data of the accelerated speed, the angular speed and the angle are obtained through the three sensors, a Bluetooth module is used for transmitting a data signal, and the signal is transmitted to a data analyzing terminal. The tumbling state is detected by analysis on various data signals through the motion sensors, and the tumbling risk is assessed and fed back to a tester by the combination with the standard of a Tinetti assessing table. The invention further discloses a gait assessment method, according to the method, through various signal types such as the accelerated speed, the angular speed and the angle, modeling is conducted on human bodies, gait characteristics are extracted, and assessment is conducted with Tinetti.