This paper shows that the transmission zeros play an important role in a system withoutsteady errors and with structurally stable properties without steady errors.From the point ofview of the frequency domain,all our discussions are based on the Smith-McMillan form oflinear multivariable systems.The engineering sense of the“internal model principle”is revealedthrough the study of transmission zeros of the systems.The main results demonstrate that alinear multivariable time-invariant system possesses structurally stable properties without steadyerrors iff every numerator polynomialε_i(s)(i=1,2,…,min(r,m))of Smith-McMillanform of the closed loop transfer function matrix from f(s)to e(s)can be divided by α_1(s),the greatest invariant factor of N(S).The property thatε_i(s)can be divided by α_1(s)isstructurally stable.