  Whether in nature exists Majorana neutrino is one of the most fundamental
questions in physics. It is directly related to the violation of accidental
$U(1)$-lepton number symmetry(LNV). Enormous efforts had been put into such
test and among them, one conventional experiment is the neutrinoless
double-beta decay ($0\nu\beta\beta$). On the other hand, there have been
proposals of future electron-positron colliders such as International Linear
Collider (ILC) for precision measurements of Higgs boson or new discovered
beyond SM particles and it can potentially be converted into an
electron-electron collider. Such collider enables a new probe of Majorana
neutrino via the inverse $0\nu\beta\beta$ process($e^{-}e^{-}\to W^- W^-$) as
an alternative and complementary test to the conventional neutrinoless
double-beta decay experiments. In this paper, we illustrate the searching
strategies of $e^{-}e^{-}\to W^- W^-$ at future electron colliders, and find
that the channels of pure hadronic, semi-leptonic with muon and pure leptonic
with muons have the most discovery potential.
