Falls accidents are one of the leading causes of older adults' injury death and nonfatal injuries. Numerous functional mobility assessment tools have been developed to evaluate the risk of fall since 1980s but none of them is fully satisfactory or generally accepted. The current study compared a promising method, the Postural-Locomotor-Manual test (PLM), with two commonly used tools, the Berg's balance test (BBT) and the timed Get-up & Go test (GU&G) in terms of their differences between healthy and fall prone groups. The PLM method measures both inherited and required motor skills as well as their coordination, by using a set of inertial measurement units (IMUs) instead of the traditional optoelectronic instruments. Results have shown that PLM parameters assessed by IMUs agreed well with those assessed by the optoelectronic instruments, and more importantly, had significant difference between groups with different fall risk.