The neutrino energy loss rate of modified URCA process in strong magnetic field of neutron star core is investigated based on the n-p-e model. Both neutron and proton branches of modified URCA process are considered. The result shows that a strong magnetic field makes the neutrino energy loss rate of modified URCA process to oscillate intensively. Compared with the neutron branch, neutrino energy loss rate of the proton branch is weaker. But the total neutrino energy loss rate will increase due to the proton branch of modified URCA processes. The result will contribute to the research of cooling mechanism of neutron stars.