We prepared Bi6Fe2Ti3O18 thin films on Pt/Ti/SiO2/Si substrates with thickness ranging from approximate to 300 to approximate to 900nm by using a chemical solution deposition route and investigated the thickness effects on the microstructure, dielectric, leakage, and ferroelectric properties of Bi6Fe2Ti3O18 thin films. Increasing thickness improves the surface morphology, dielectric, and leakage properties of Bi6Fe2Ti3O18 thin films and a well-defined ferroelectric hysteresis loops can form for the thin films with the thickness above 400nm. Moreover, the thickness dependence of saturation polarization is insignificant, whereas the remnant polarization decreases slightly with increasing thickness and it possesses a maximal value of approximate to 20 C/cm(2) for the 500nm-thick thin films. The mechanisms of the thickness dependence of microstructure, dielectric, and ferroelectric properties are discussed in detail. The results will provide a guidance to optimize the ferroelectric properties in Bi6Fe2Ti3O18 thin films by chemical solution deposition, which is important to further explore single-phase multiferroics in the n=5 Aurivillius thin films.