  We have constructed a preonic model starting from a coloured fermionic preon
and by postulating a new symmetry, MUSY. This new symmetry is defined via the
MU number involving colour, charge and spin properties of the preons. We show
that all the known fields of the Standard Model (SM) can be constructed using
the fermionic preon and 6 preonic scalars, its MUSY partners. As an example, we
present well known \beta-decay process at MUSY level. MUSY also forbids some
processes such as proton decay (preserving the baryon number) and hence, it is
compatible with current experimental results. In this model the number of SM
generations arises to be three naturally.
  The MUSY generalization of the SUSY algebra is constructed and the MUSY
invariant Lagrangian is also explicitly written. Similar to other preonic and
supersymmetric models, a number of new particles are predicted. These particles
do not interact with any of the SM fermions but only with the gauge bosons.
These particles could be dark matter candidates.
