The invention discloses wear-resistant steel with 400-level Brinell hardness and a manufacturing method thereof. The steel comprises, by mass, 0.14-0.21% of C, 0.20-0.40% of Si, 0.9-1.4% of Mn, 0.015% of P or less, 0.008% of S or less, 0.5-0.8% of Cr, 0.05-0.08% of Ni, 0.2-0.4% of Mo, 0.02-0.05% of Als, 0.02-0.03% of Ti, 0.02% of V or less, 0.005% of B or less, and the balance iron and inevitable impurities. The manufacturing method includes the following steps that the chemical components are proportionally subjected to vacuum melting and cast into blanks, and then plate blank heating, rolling, cooling, quenching and low-temperature tempering are performed to obtain finished steel plates. The wear-resistant steel is good in residual stress uniformity, free of cracking or deformation in the use process, resistant to wear and long in service life.