Geosynthetic materials are broadly adopted in geotechnical, transportation, environmental, and hydraulic engineering, such as roadway and railway stabilization and reinforcement, pavement solutions, retaining wall stabilization and landscape, embankments stabilization and differential settlement limitation, landfill and waste containment drainage and filtration enhancement, and steep slope solutions. The use of geosynthetic materials may lead to significant savings in material costs and construction time when they can be used instead of traditional materials and construction methods. Recently, more and more government agencies and highway/bridge engineers have found the need to get familiar with the background knowledge, design methodologies and construction practices of the geosynthetic materials, especially the geosynthetic reinforced steep slopes. This paper educates bridge and geotechnical engineers by reviewing the basic concepts, histories, applications, and researches of geosynthetic materials, demonstrating detailed case studies on the design and construction practices of geosynthetic reinforced steep slopes, and introducing the basic failure mechanisms for the geosynthetic reinforced steep slopes. Furthermore, this paper explores optimum design for the geosynthetic reinforced steep slopes and recommends that the optimum design of geosynthetic reinforcement could be easily obtained with a 10 degree backfill slope angle or a horizontal crest length larger than or equal to half of the total slope length.