The strain hardening behaviors of 32Mn-7Cr-1Mo-0.3N austenitic steel were characterized by a simple and effective method. The results show that Hollomon relationship is not applicable during total uniform deformation stage. The flow equation was proposed, lnσ=aexp(lnε/b)+c. The variation rates of strain hardening exponents with true strain at 77 K are obviously higher than that at other temperatures and the value of d2σ/dε2 becomes positive during high strain stage. The characters of this variation are principal reasons for increasing elongation at 77 K. The forming of mechanical twin as well asε-martensite leads to a high elongation at 77 K. The strain hardening behaviors of 32Mn-7Cr-1Mo-0.3N austenitic steel were characterized by a simple and effective method. The results show that Hollomon relationship is not applicable during total uniform deformation stage. The flow equation was proposed, lnσ = aexp (lnε / b) + c. The variation rates of strain hardening exponents with true strain at 77 K are obviously higher than that at other temperatures and the value of d2σ / dε2 becomes positive during high strain stage. The characters of this variation are principal reasons for increasing elongation at 77 K. The forming of mechanical twin as well asε-martensite leads to a high elongation at 77 K.