High-power nanosecond fiber lasers have been widely used in laser engraving. In this paper, the effects of pulse width, energy density, and pulse repetition frequency (PRF) on laser engraving results are studied by using a master oscillator power amplifier (MOPA) fiber laser system, with carbon steel as the research material. The material removal rate (MRR) and average surface roughness (S_a) of each group of parameters are measured by a three-dimensional (3D) profilometer. It is found that longer pulse width and higher energy density can result in larger MRR and Sa. Larger MRR and S_a can also be obtained with short pulse width and high energy density, which is caused by a high pulse overlap rate. There is a critical PRF that can simultaneously make MRR large and S_a small. Finally, the optimized process parameters are used to achieve the engraving effects of high quality and high MRR.