We demonstrate experimentally a method to measure breakpoints and impedance mismatch for dielectric transmission lines by using broadband chaotic signals. Chaotic signal serving as a probe signal is obtained from the chaotic laser diode with optical feedback. Correlation method can realize breakpoint location, impedance estimation, and live test. Experimental results show that the location deviation is less than 1%, the impedance error is within the nominal rating, and interference margin is about 48 dB for 2 MHz square pulse signal on wire.