In the present study, (1 − x)BaAl 2 Si 2 O 8 −xCaSnSiO 5 −y wt.% LiF microwave dielectric ceramics were prepared through the traditional solid-state sintering at 950−1395 • C for 5 h. The BaAl 2 Si 2 O 8 phase could coexist with the CaSnSiO 5 phase at (1 − x)BaAl 2 Si 2 O 8 −xCaSnSiO 5 (.2 ≤ x ≤ .6) ceramics, and no other secondary phase was observed. The CaSnSiO 5 , as a τ f regulator, adjusted the negative τ f value of BaAl 2 Si 2 O 8 to near zero. Excellent microwave dielectric properties (ε r = 8.1, Q × f = 37 560 GHz, and τ f = −1.5 ppm/ • C) were obtained from the 0.6BaAl 2 Si 2 O 8 −0.4CaSnSiO 5 ceramic. The sintering temperature of 0.6BaAl 2 Si 2 O 8 −0.4CaSnSiO 5 ceramic decreased from 1375 • C to 950 • C by introducing 2 wt.% LiF. The 0.6BaAl 2 Si 2 O 8 −0.4CaSnSiO 5 −2 wt% LiF ceramic exhibited remarkable microwave dielectric properties (ε r = 7.6, Q × f = 17 420 GHz, and τ f = −12.2 ppm/ • C) and could be applied to the low-temperature co-fired ceramic (LTCC) field. K E Y W O R D S (1 -x)BaAl 2 Si 2 O 8 −xCaSnSiO 5 ceramic, LTCC applications, microwave dielectric properties, phase transition 1 480