This paper proposes a novel box-particle multipath cardinality balanced multitarget multi-Bernoulli (BP-MPCBMeMBer) filter for the problem of multitarget tracking in Over-the-horizon radar (OTHR). The proposed algorithm combines the multipath cardinality balanced multitarget multi-Bernoulli (MPCBMeMBer) filter with interval analysis to solve the problems of high computational complexity and nonlinear measurement models. First, establishment of the OTHR measurement model based on interval analysis, and then the box-particle filter is used to derive the BP-MPCBMeMBer based on the original MPCBMeMBer filter. Eventually, the simulation results are presented to verify the effectiveness of the BP-MPCBMeMBer filter.