  A pants-block decomposition of a 3-manifold is similar to a triangulation of
a 3-manifold in many aspects. In this paper we show that any two pants-block
decompositions of a 3-manifold are related by a finite sequence of moves which
are called P-moves. The P-moves between pants-block decompositions are similar
to the Pachner moves between triangulations. Moreover, we also give a list of
types of P-moves. The main tools we used in this paper are the Morse
2-functions, Reeb complexes and a new 2-dimensional complex called P-complex.
