The interactions in multiple D-PMSGs-gridding systems are quite complex, and it is difficult to determine the oscillation paths and dominant oscillation sources. To solve this problem, the transfer function method of multiple input and multiple output is adopted, and the interactions in multiple D-PMSGs-gridding systems are analyzed. First, a system example of 4 D-PMSGs and 5 nodes is established, and the transfer matrix model is obtained. Secondly, the interaction between D-PMSGs and grid and the interaction between different D-PMSGs is analyzed. Then, the oscillation path and oscillation source are determined. Finally, targeted optimization measures are proposed, which are optimization of cutting D-PMSG and optimization of parameters, and it is verified by using eigenvalue method and time-domain simulation method.