The utility model discloses a street lamp circuit cable antitheft detection's device under the not power supply circumstances comprises circuit starting point end and the terminal two parts circuit of circuit. Wherein the detection of the applying of DC signal, circuit connectivity is mainly accomplished to starting point end circuit, the terminal circuit part is mainly accomplished the automatic of terminal resistance and is dropped into and the excision. The utility model discloses under street lamp circuit not power supply on the daytime circumstances, insert a terminal resistance between circuit terminal point L, N, DC signal is exerted to the starting point on L, two finding activate ways of N to the real -time detection circuit is continuous or has been cut off, thereby whether accurate judgement street lamp circuit is stolen by people's destruction, and this device is simple reliable, easy to carry out.