Serrated flow and work-hardening behavior (by Voce equation) of China low activation martensitic (CLAM) steel were investigated in the temperature range of 300–923 K (27 °C to 650 °C). The steel exhibited serrated flow at intermediate temperatures of 573–623 K (300–350 °C) and elevated temperatures higher than 773 K (500 °C), respectively. Type A, A + B, A + C, A + D, and mild serrations were identified. The observed serrations, the plateau/peak in flow stress and a minimum in ductility suggested the occurrence of dynamic strain aging (DSA), a phenomenon due to interactions between solute atoms and dislocations during plastic deformation, at intermediate temperatures, while the mild serrations observed at high temperatures were ascribed to a combined effect of tensile deformation and dynamic recovery. The variations of work-hardening parameters including saturation stress ${\mathsf{\sigma }}_S$ , initial stress ${\mathsf{\sigma }}_I$ and rate parameter $n_V$ with respect to temperatures also implied the dominance of DSA at intermediate temperatures. CLAM steel in present investigation generally displayed two-stage work-hardening behavior consisting of transient stage and stage-III. Good correlations had been presented between work-hardening parameters obtained by Voce equation and the respective experimental tensile properties, suggesting adequate applicability of Voce relationship for CLAM steel.