-In this paper, we extend the previous results on trajectory linearization observer (TLO) for SISO to MIMO nonlinear time-varying (NLTV) systems, and extend the highgain observer theory for linear time-invariant (LTI) observer error dynamics to linear time-varying (LTV) observer error dynamics, using the (time-varying) PD-eigenvalue assignment method. In addition, the time-varying high gain TLO alleviates the slowly varying restriction, and relaxes the restriction of existing time-invariant nonlinear high gain observer to affine nonlinear systems to allow for any linearizable NLTV system.