In a certain magnetic field, spin exchange collision is one of the limiting factors for coherence preserving in atomic magnetometers, which directly affects the detection sensitivity that the magnetometer can achieve. The light narrowing effect can be used to reduce the resonance linewidth caused by spin-exchange collisions. Previous observations of the light narrowing effect are based on atomic magnetometers with continuous pumped laser and radio frequency field, which have additional effects on the atomic resonance linewidth. Based on a pulse-pumped atomic magnetometer, the effects of atomic destructive collisions and magnetic field inhomogeneity on resonance linewidth are greatly reduced, and a direct experimental observation and verification of the light narrowing effect are realized. As pulse-pumped mode is beneficial to the realization of high atomic polarization, the study of light narrowing effect is of great importance for exploring the sensitivity limit of pulse-pumped atomic magnetometers.