To comprehend the mechanism of multi-sensor passive localization thoroughly and then improve its localization precision, several related issues in dual-sensor bearing-only localization are theoretically analyzed. First the factors that can affect the dual-sensor localization performance are studied, which indicate that only when the measurement error is small enough and the cut angle between the sensors is not close to 0 and π, the dual-sensor system is unbiased and may be consistent. Next we point out that the negative impact of small enough cut angle on the localization precision is greater than that of large enough cut angle when they have the same magnitudes in terms of 0 and π. Finally, the equivalence of two localization error covariance methods is analyzed. Simulation results verify the above analysis, which indicate that the corresponding conclusions can be applied to multi-sensor passive localization algorithms based on sensor management.