LiNb$_{1-x}$TaxO3 thin films were successfully deposited on Pt(111)/Ti/SiO2/Si(100) substrates by spin coating with a diol-based sol-gel technology and rapid thermal annealing. The effects of various processing parameters, including Ta content (0$\leq x\leq1$) and heating temperature (500 ~ 800 °C), on the growth and properties of thin films were investigated. With the increase of Ta content, the grain size of film decreased slightly, and the maximum f factor (the degree of c-axis orientation) of the films were obtained in the composition of x = 0.2. As the composition of film varied from x = 0 to x = 1, the relative dielectric constant of film increased from 33 up to 62, and the dielectric loss factor (tanδ) also increased from 0.00374 to 0.00686, respectively. The coercive field, Ec, and remanent polarization, Pr, decreased but pyroelectric coefficient, γ, increased from 2.76 × 10−8 up to 4.51 × 10−8 C/cm2 K. The pyroelectric figures of merit, Fv and Fm, indicated that film with Ta content of 20 mol% and heating temperature of 700 °C exhibited the optimized pyroelectric characteristics and could be applied for high-performance pyroelectric thin-film detectors.