Bloomfield has pointed out that the kink structure occurs for sharp bending during DNA condensation process, until now, which has not been proved by experiments. Using UV Spectrophotometer, the effects of fluoride and chlorine on the polyamine-DNA condensation system can be detected. Fluoride and chlorine both belong to the halogen family, but their effects on spermine-DNA condensation system are totally different. Fluoride ions make blue-shift and hyperchromicity appear in the spermine-DNA condensation system, but chlorine ions only make insignificant hyperchromicity happen in this system. Both fluoride ions and chlorine ions only make insignificant hyperchromicity happen in spermidine-DNA condensation system. Based on the distinguished character of fluoride, a fluoride-sensor for “kink” structure in DNA condensation was developed and the second kind of “kink” structure only appear in the spermine-DNA condensation system.