The resource leveling problem is a class of classical project scheduling problems, which aims at leveling the resource usages over the project horizon by scheduling activities. Because of the theoretical importance and the practice background, the resource leveling problem has been attracting many research efforts. Therefore, a literature review of the research on the area of resource leveling is proposed. Firstly, the mathematical model of the resource leveling problem and some standard test instances are introduced. The algorithms for solving the resource leveling problem are reviewed. The extensions and applications of the resource leveling problem are surveyed. Finally, some future research directions are presented.