The utility model relates to a detector for rank analysis, in particular to a detector for the rank analysis of the salt deposit density and the hydrophobicity of insulators for power transmission and distribution, and belongs to the detection devices for supervising insulation in the technical field of the electric transmission line. The detector comprises an LED, a light dependent resistor, a potentiometer, a display drive, a display, an SCM, a triode, a power supply and a switch, wherein the light dependent resistor and the potentiometer are connected in series; the series-connected branch is connected with the LED in parallel and is then connected with both ends of the power supply; the base electrode of the triode is connected with the common terminal of the light dependent resistor and the potentiometer; the emitting electrode of the triode is connected with the negative pole of the power supply; the collecting electrode of the triode is connected with the SCM; the SCM is connected with the display through the display drive; the switch, the SCM and the display drive are connected with the power supply. The detector has the advantages that no detaching or attaching is needed, so that the contamination adhered on the insulators to be tested can be prevented from dropping off from the insulators when the insulators are carried; the analysis accuracy of the salt deposit density and the hydrophobicity of the insulators is enhanced; the work intensity of the testers can be greatly reduced while the work efficiency is enhanced.