Falls are the second leading cause of unintentional injury deaths worldwide, so how to prevent falls has become a safety and security problem for elderly people. At present, because the sensing modules of most fall alarms generally only integrate the single 3-axis accelerometer, the measurement accuracy of sensing signals is limited. They can only achieve the alarm of post-fall detection but not the early pre-impact fall recognition in real fall applications. Therefore, an early preimpact fall alarm system based on high-precision inertial sensing units was studied and developed in this paper. A multimodality sensing module embedded with the fall detection algorithm was developed for the early pre-impact fall detection. The module included a 3-axis accelerometer, a 3-axis gyroscope and a 3-axis magnetometer, which could arouse early preimpact fall warnings by a buzzer and a vibrator. Total 81 times of fall experiments from 9 healthy subjects were conducted in simulated fall conditions. The result shows that the detection sensitivity of the system combining the early warning threshold algorithm can reach 98.61% with a specificity of 98.61%, and the average pre-impact lead time is 300 ms. In the future, GPS, GSM electronic modules and wearable protected airbags will be embedded in the system, which will enhance real-time fall protections and timely treatments for the elderly people.