The optic sensor salt density on-line monitoring system is a new technology of on-line monitoring insulator pollution. Due to the baffle above, the optic sensor salt density on-line monitoring system is not obvious to the reflection of rain. In this paper, the original equipment is improved, that is, double optic sensor salt density on-line monitoring system. When continuous shower or heavy rain, it has response that the equivalent salt deposit density measured by the light sensor. By analyzing the measured data, the basic data obtained from the measurement are almost the same, while by comparing the data, it is the same that the overall trend of the measurement data obtained by the upper sensor and the insulators. finally, the necessity and feasibility of the system are verified.