  A Monte Carlo method is presented to evaluate quantum states with many
particles moving in the continuum. The scattering state is generated at each
time by a Monte Carlo random sampling algorithm. The same calculation are
repeated until the average energies of all calculations converge. For systems
with one and a few particles, our calculations show that the exact solution can
be approached with around only one hundred iterations. As examples, we apply
the approach to study the structure of neutron-rich oxygen isotopes.
