In several substations of the Central Tibet Linking Project, SVC is used to improve the voltage control features in weak-link power grid. According to electromagnetic transient simulation, improper control parameters of SVC may lead to a novel sub-synchronous oscillation in weak-link power grid. According to further studying the character and suppressing method of this novel sub-synchronous oscillation, a linearized electromagnetic transient model of SVC and power grid is promoted, eigenvalue analysis method is applied to analyze two test systems. The results show that this novel sub-synchronous oscillation happens in a system which has a sub-synchronous mode, improper control parameter of SVC decreases the damping of the sub-synchronous mode, therefore leads to sub-synchronous oscillation. These damping decreasing effects caused by several SVCs are superposed, increasing the probability of sub-synchronous oscillation. Finally, several suppression measures are proposed according to the characters of this novel oscillation. This work is supported by National Key Research and Development Program of China (No. 2018YFB0905200) and Science and Technology Project of State Grid Sichuan Electric Power Company (No. 52199718001W).