Ca/P-doped TiO₂ nanofibers were produced via sol-gel electrospinning technique and used for the electrochemical detection of guanine and oxidaiton of ssDNA molecules. The nanofibers first morphologically analysed with scanning electrone microscopy (SEM). Fiber diameters decreased after the calcination process at both neat and Ca/P-doped samples. Fiber uniformatey was too much deterioarted after the calcination process at Ca/P-doped sample. Elementel analysis were carried out with EDX measurement and crystal structure of the nanofiber were investigated via X-ray diffraction method. XRD results revealted that evet though just anatase and rutile TiO₂ cryatslas were detected at neat TiO₂ nanofibers, Ca/P related crystalline peaks were also appeared after Ca/P doping. The crystallinity of TiO₂ decreased with Ca/P doping. EDX spectra also confiremed the existence of Ti, O and Ca/P in Ca/P-doped TiO₂ nanofibers. Ca/P-doped TiO₂ nanofibers were immobilized on SPE with single strand DNA molecules (ssDNA), and the DPV measurement were performed. The measurement were carried out under dark condition, solar and UV light irridations. Guanine and adenin oxidaitons were observed by immobilizing ssDNA molecules on SPEs with the prepared Ca/P-doped TiO₂ nanofibers. The results revealed that the intensities of guanine and adenine oxidaiton peaks were increased when Ca/P-doped TiO₂ nanofibers were used.