Reciprocating force signal is usually non-stationary.The empirical mode decomposition(EMD)method can decompose these nonlinear and non-stationary signals adaptively,and extract the signal characteristics reasonably.The force signals of reciprocating movement under different speed and load conditions were analyzed by applying Hilbert-Huang transform(HHT)method,the energy ratio of time-frequency band and its standard deviation was extracted to study the lubrication state characteristics of reciprocating movement.The result shows that HHT combined with the energy ratio analysis is a very good way to reflect the variation of lubrication condition in the process of reciprocating movement.Under certain load condition,the friction frequency is tended to be stabilized,and the standard deviation of energy ratio is decreased with increasing of reciprocating speed.At a certain reciprocating speed condition,the lubrication state is gotten worse,and the consumption of energy is increased,but the standard deviation of energy ratios is decreased gradually along with increasing of the loads.As compared with reciprocating speed,the load has smaller effect on friction frequency distribution.