Recent five years, according to statistic data of flight safety, it indicated the five year's hull loss rate of the civil helicopters is 4.3 times per ten-thousand departures, which is greater than 60 times of U.S.A. and European record. The common types of accidents are controlled flight into terrain, loss of control in-flight, and proximity to ground obstacles or other aircraft. This paper reviewed the development and evolution of helicopter health management and flight data monitoring systems in the last 20 years. Refer to the relevant technical documents of the Intl' Helicopter Safety Working Group and UK CAA's helicopter airworthy regulation. To discuss the parameters setting criteria for the flight data monitoring system. Based on the initial study results of helicopter flight data, to explain unstable approach events, and unsafe operations may be related to autorotation events. Author wishes that the shallow study results from this paper can throw light on the further researchers, aviation community should pay more attention to helicopter safety issues, invest more resources for the development of flight data monitoring technologies, and joining together to improve the flight safety level of Taiwan.