Objective To propose a novel classification of L₅ spondylolysis and spondylolisthesis in children based on surgical treatment and to explore its availability. Methods A total of 47 children with L₅ spondylolysis or spondylolisthesis, who underwent surgical treatment in Changzheng Hospital of Naval Medical University (Second Military Medical University) between Jan. 2012 and Sep. 2017, were retrospectively included. According to the severity of spondylolisthesis (Meyerding grade), the degree of L₅/S₁ disc degeneration (Pfirrmann grade) and dysplastic features (classification described by Mac-Thiong and Labelle), a novel classification of L₅ spondylolysis and spondylolisthesis based on surgical treatment was proposed. This classification contains four types. Type Ⅰ:using pedicle screw-U rod system to repair the isthmic defect without segment fusion. Type Ⅱ (single-segment L₅/S₁ fusion type):requiring posterior L₅/S₁ fusion and internal fixation. Type Ⅲ (doublesegment L₄-S₁ fusion type):using pedicle screw system to perform L₄-S₁ reduction, decompression, fusion and internal fixation. Type Ⅳ(multi-segment L₅-S₂ fusion type):using pedicle screw system to perform L₅-S₂ reduction, decompression, fusion and internal fixation. Lumbar Japanese Orthopaedics Association (JOA) score and Oswestry disability index (ODI) were evaluated before and after surgery. Results There were 13 cases of type Ⅰ (8 males and 5 females), 14 cases of type Ⅱ (6 males and 8 females), 11 cases of type Ⅲ (4 males and 7 females), and 9 cases of type Ⅳ (3 males and 6 females). The average ages of type Ⅰ, Ⅱ, Ⅲ and Ⅳ patients were (14.6±2.1), (15.7±2.4), (13.2±2.3) and (14.6±3.2) years old, respectively. The lumbar JOA score and ODI were improved two years after surgery compared with those before surgery in type Ⅰ, Ⅱ, Ⅲ and Ⅳ patients (JOA score 19.2±2.1 vs 14.7±2.5, 20.2±1.9 vs 14.3±2.4, 21.1±2.2 vs 13.3±2.4, and 20.7±1.9 vs 11.8±2.4; ODI[16.1±1.8]% vs[56.2±1.7]%,[14.7±1.7]% vs[54.8±1.8]%,[13.7±2.2]% vs[55.7±2.4]%, and[12.9±1.7]% vs[52.5±2.3]%), and the differences were significant (all P<0.01). Conclusion A novel classification of L 5 spondylolysis and spondylolisthesis in children is proposed, and it can better guide the surgical treatment. Pedicle screw-U rod system is more effective in the treatment of simple L₅ spondylolysis, and fusion from L₅ to S₂ is more suitable for L 5 spondylolysis and spondylolisthesis patients with high-degree dysplasia.