There is polarization phenomenon in theinorganic ferroelectric perovskite oxides [KNbO₃]1-x[BaNi1/2 Nb1/2 O₃-δ]x（KBNNO）, which could form the built-in electric field and accelarate the separation of photo-induced carriers. However, the inorganic ferroelectric perovskite oxides holds wide optical band gap and exhibits low conductivity, which hinders the transportation of photo-induced carrier. To our joy, transition-metal doping is a fruitful method to reduce the bandgap of ferroelectric perovskite and enlarge the absorption edges. Additionally, one-dimensional Ti O₂ exhibits excellent ability of electron transmission and has been applied in the field of solar cells. Therefore, the composite of inorganic ferroelectric perovskite oxides and matal oxide semiconductor material could combine advantages of both two materials. Given their fascinating potentials, surprisingly, hardly any work about these materials has been explored in the field of PEC bioanalysis. We report the synthesis of [KNbO3]1-x [BaNi1/2 Nb1/2 O3-δ]x（KBNNO） solid solutions（0.1 ≤ x ≤ 0.5） by doping Ni and Ba into the lattice of orthorhombic KNbO₃ though solid-state reaction. The bandgap of above two materials has been lowered to 1.1 eV, respectively. Subsequently, we adopted pulsed laser deposition technique to deposit film on TiO₂ NRs and finally prepared the compound KBNNO@TiO₂ NRs. The results show that the current density of KBNNO@TiO₂ NRs（x = 0.3） photoanode are 5.1 times as high as bare Ti O₂ nanorods photoanode, respectively. The reason of improvement of energy conversion performance is that Ni/Ba-doping and Co/Ba-doping in KNO could diminish the bandgap and the oxygen vacancies can serve as photoinduced charge traps and adsorption sites, preventing recombination of photoinduced electron-hole. In the detection of L-Cysteine, the as-fabricated KBNNO@TiO₂ NRs demonstrated good performance in terms of sensitivity and selectivity. This work unveiled the promise of ferroelectric perovskite oxide and its based heterostructures for innovative PEC bioanalytical application and we hope it could inspire more interests in the development of various ferroelectrics-based heterostructures for advanced PEC bioanalysis.