K0.5Na0.5NbO3 thin films with (K,Na) excess and LiNbO3 substitution were fabricated on a Pt substrate by a chemical solution deposition method. The K0.5Na0.5NbO3 thin films with (K,Na) 10 mol % excess and LiNbO3 5 mol % substitution showed a saturated ferroelectric polarization–electric field (P–E) hysteresis loop and the estimated remanent polarization (P
r) and coercive field (E
c) were 8.6 µC/cm2 and 40 kV/cm at 280 kV/cm, respectively. Compared to pure K0.5Na0.5NbO3 thin films, the ferroelectric polarization of the thin film was improved and leakage current densities were decreased. Moreover, the ferroelectric polarization and leakage current characteristics are stable for higher applied electric fields and elevated temperatures. The conduction behaviours of these films were analyzed by Schottky and Poole–Frenkel emission.