The paper used the MCNPX software to calculate the efficiencies and counting rate of a same size of LaBr3 (Ce) scintillation crystals detector for β+ particle in different size of MB Beaker, and different size of LaBr3 (Ce) scintillation crystals detector for same MB Beaker, and same size of LaBr3 (Ce) scintillation crystals detector but in different depth in the same MB Beaker. Based on the result, the optimal volume of MB Beaker and the optimal depth in MB Beaker was assured, then compared with the data attained in analog computation for NaI...