Abstract: The manganese bath method is a commonly used method for determining neutron source emission rate.The Monte Carlo method (MCNP) was used to calculate the influence of main parameters such as bath radius, MnSO₄ solution density, and measurement chamber volume on neutron capture fraction, leakage fraction, and detector count rate in a manganese bath facility. The activation count rate for measuring neutron source emission rate was also calculated for different sizes of bath and measurement chamber. Based on the calculation results, a movable manganese bath facility was established, which achieved a counting rate approximately 11.5 times higher than the primary manganese bath facility when measuring ²⁴¹Am-Be neutron source, therefore the measurement range was expanded by approximately one order of magnitude. Two low emission rate neutron sources were measured by movable manganese bath facility, which emission rate is 4.09×10⁴ s⁻¹ and 1.75×10⁵ s⁻¹, respectively. The standard uncertainty is less than 1.5%.