If the structure of wind turbine generator's drive train model is too simplified, it may not reflect the subsynchronous oscillation (SSO) mode. The types and sizes of wind turbine generator (WTG) are various. Therefore, the parameters of drive train model vary widely. There is an urgent need to study the effects of drive train model's structures and parameters on SSO. In this paper, mass-spring-damping shaft models of WTG are presented. Eigenvalue analysis is used to study the effects of drive train model on SSO. The results show that, if two-mass model is adopted, only the low-frequency oscillation (LFO) exists. If three-mass model is adopted, there will be the LFO and SSO. In inertial constants, the inertia of hub (H-h) has the greatest effect on SSO. With the increasing of H-h, the frequency and damping of SSO decrease. In spring constants, the spring constant between hub and generator (K-hg) has the greatest effect on SSO. With the increasing of K-hg, the frequency of SSO increases, yet the damping decreases. In damping constants, the damping constant of hub (D-h) has the greatest effect on SSO. With the increasing of D-h, the damping of SSO increases. Damping constants almost have no effect on the frequency of SSO.