The true stress-strain curve of the metal beryllium was obtained under deformation temperature of 250 ℃~450 ℃ and strain rate of 10_-1 ^s_-1^-10_-4 ^s_-1 by the isothermal compression testing which was conducted in the Instron 5582 universal material testing machine, and thus flow behaviors of the metal beryllium was studied in the first plastic peak zone. The results indicate that the flow stress of the metal beryllium increases with the increase of strain rate and decreases with the increase of deformation temperature under the experimental conditions. Furthermore, the flow stress is more sensitive to the variation of temperature. The flow stresses show a decreasing trend with the increase of strain after work hardening to a certain extent under various deformation conditions, especially 250 ℃/10_-1 ^s_-1^, theSflowSstressShasSaSpeakSvalue. Moreover, the deformation activation energy of the metal beryllium decreases from 244.95 kJ/mol to 166.82 kJ/mol as the strain increases. These results indicate that softening mechanism of the metal beryllium deformed in the first plastic peak zone is influenced by dynamic recrystallization, but the main softening mechanism is still recovery. It was established that an Arrhenius strain compensated constitutive equation that includes strain variables. The equation can accurately predict the flow stress of the metal beryllium during compression deformation in the first plastic peak zone, and the maximum mean relative estimation error (MRE) of the prediction is 5.0550%, and the minimum correlation coefficient (R) is 0.9899.