A non-contact vital sign sensing system including a vital sign sensing module and at least one body movement interference cancellation module is provided. The vital sign sensing module and the at least one body movement interference cancellation module are under a self-injection locking (SIL) mode. The vital sign sensing module senses an isotropic vital sign of a body. A mutual injection locking (MIL) mode is achieved between the vital sign sensing module and the at least one body movement interference cancellation module to sense the anisotropic body movement signal and to cancel the body movement interference.
