  We extend the matrix decomposition method(MDM) in classifying the $2\times
N\times N$ truly entangled states to $2\times M\times N$ system under the
condition of stochastic local operations and classical communication. It is
found that the MDM is quite practical and convenient in operation for the
asymmetrical tripartite states, and an explicit example of the classification
of $2\times 6\times 7$ quantum system is presented.
