In this paper, the results on the parameterization of all the unfalsified models for single-input/single-output systems are extended to multi-input/multi-output systems. In this arameterization, the assumed a priori plant and noise information are upper bounds of the Hx-norm of the plant matrix-valued transfer function and the noise magnitude. The parameterization is on the basis of several series of plant time-domain identification experiment data. It is shown that for multi-input/multi-output systems, all the unfalsified plant matrix-valued transfer functions can still be expressed by the linear fractional transformation of a fixed matrix-valued transfer function and an Hx-norm bounded structure fixed, but uncertain matrix-valued transfer function. However, the high dimensions of the matrix-valued transfer functions involved in the parameterization hamper the direct application of these results to robust controller design. To overcome these difficulties, further efforts are needed.