  Since particle such as molecule, atom and nucleus are composite particle, it
is important to recognize that physics must be invariant for both the composite
particle and its constituent particles, this requirement is called particle
invariance. But difficulties arise immediately because for fermion we use the
Dirac equation, for boson we use the Klein-Gordon equation. Therefore, the
particle invariance demands there is a general wave equation for describing
particle motion regardless particle class. In this paper, three advances in
this subject are reported: (1) momentum-wavefunction relation is a general
relation shared by both fermion and boson, meets the requirement of the
particle invaiance. As a test, the momentum-wavefunction relation was directly
applied to hydrogen atom, and get the correct fine structure and spin effect
for the electron. (2) the Dirac equation and Klein-Gordon equation can be
derived out from the momentum-wavefunction relation when we abandon some higher
order terms. (3) according to the momentum-wavefunction relation a path
integral method was developed, differing from Feynman's path integral, it
simplfies quantum computation.
