Take electronic ballast of UV intensity detection includes the UV lamp that is used for clean water sterilization, still includes the UV sensor, with UV's parallelly connected setting, when the UV lamp starts, the UV sensor gets electricly and gathers current ultraviolet intensity with output sample voltage, reference cell for output reference voltage, comparing element is coupled in UV sensor and reference cell, according to reference voltage and sample voltage comparison, and when sample voltage is less than reference voltage, the comparing element alarm output signal, the alarm unit is coupled in comparing element, in response to alarm signal work, output alarm signal when sample voltage is lighter than reference voltage, it is not ideal that this alarm unit gets electric bactericidal effect in order to remind this UV lamp of staff in response to alarm signal, need take measures.