This invention belongs to the field of metallurgical technology, and particularly relates to a 420MPa grade galvanized low-
alloy high-strength steel and its production method. The steel composition by
mass percentage is as follows: C: 0.06%~0.08%, Si: 0.05%~0.08%, Mn: 0.95%~1.15%, P≤0.025%, S≤0.010%, Al: 0.015%~0.060%, O≤0.0060%, N≤0.0060%, V: 0.01%~0.03%, Ti: 0.01%~0.03%, with the balance being Fe and unavoidable impurities. The advantages are: through V-Ti composite microalloying and controlled hot and cold rolling processes, synergistic effects of
fine grain strengthening and
precipitation strengthening are achieved. The
ferrite grain size is 2~5μm, the (Ti,V)C precipitate size is 20~30nm, the steel plate yield strength is ≥420MPa, and the elongation is maintained above 20%.