The segment wavemaker is an important laboratory equipment in the study of properties of wave and the stimulation of real sea wave.Relative width of wavemaker and wave period are significant factors which influence the quality of waves generated by segment wavemakers.The theoretical properties of oblique wave generated by segment wavemakers are studied through numerical model.The influence of wave period and relative width of wavemaker on wave propagation is analyzed,and the variation of effective test area of serpent-type wavemakers is concluded.The results may serve as reference for the practical use.