In order to explore the selectivity of different mesh size codends for Trichiurus lepturus, the covered net method was adopted, and selection experiments were carried out with 5 different mesh sizes(35,45,55,60 and 65 mm) codends on canvas spreader stow net. The Logistic selection model was used to fit the selectivity curve of Trichiurus lepturus and the model parameters were estimated by the maximum likelihood method. The results showed that:(1) 4 265 ind. of Trichiurus lepturus were measured during the experiment, the anal length ranged from 76-305 mm with an average anal length of (167±43) mm; (2) When the mesh size was 35 mm, it was non-selective for Trichiurus lepturus. While the mesh size was 65 mm, the distribution of anal length of Trichiurus lepturus in covered and codend net was basically the same. With the increase of mesh size, the dominant body length of Trichiurus lepturus in the codends was larger than that of the covered nets; (3) When the mesh size for Trichiurus lepturus was 45,55 and 60 mm,its L₅₀ was 171.839,180.562 and 215.905 mm, its SR was 60.402,104.861 and 157.292 mm, respectively. L₅₀ showed a gradual increase trend; (4) The relationship between the codend mesh size(m) of Trichiurus lepturus and L₅₀:L₅₀=2.643m+48.491 (R²=0.748); (5) When the anal length of Trichiurus lepturus is 210 mm, the minimum mesh size of canvas spreader stow net should be 61.1 mm. In summary, combined with the current status of fishery resources, the current minimum mesh size of 55 mm is more appropriate to protect the juvenile Trichiurus lepturus resources, which can achieve the aim of protecting the juvenile Trichiurus lepturus resources.