Ba0.6Sr0.4TiO3 (BST) thick films were fabricated on Al2O3 substrate via the screen printing technology by using B2O3–Li2O additions as liquid-phase sintering aids. The effects of doping of B2O3 and Li2CO3 on the phase compositions, microstructures, and dielectric tunable properties of the thick films were investigated systematically. The X-ray diffraction patterns showed that BST diffraction peaks shifted toward higher angle with the B2O3–Li2O doping content, which indicated the substitution of B3+ and Li+ in Ba2+ site. It was also found that the grain size and electrical properties of the thick film were strongly affected by the glass content. The grain size and the relative permittivity decreased obviously with the increase of B2O3–Li2O additive. In addition, for the thick film with 4.5 wt% glass content, optimized sintering, and electrical properties were obtained: the sintering temperature of 900 °C, relative permittivity of 312 (at 10 kHz), dielectric loss of 0.0039, tunability of 16.2% (at 3 kV/mm). These good sintering and electrical properties indicate that BST thick film with B2O3–Li2O addition is benefit for the development of LTCC technology and tunable devices.