In the present study, (1 − x)BaAl2Si2O8−xCaSnSiO5−y wt.% LiF microwave dielectric ceramics were prepared through the traditional solid‐state sintering at 950−1395°C for 5 h. The BaAl2Si2O8 phase could coexist with the CaSnSiO5 phase at (1 − x)BaAl2Si2O8−xCaSnSiO5 (.2 ≤ x ≤ .6) ceramics, and no other secondary phase was observed. The CaSnSiO5, as a τf regulator, adjusted the negative τf value of BaAl2Si2O8 to near zero. Excellent microwave dielectric properties (εr = 8.1, Q × f = 37 560 GHz, and τf = −1.5 ppm/°C) were obtained from the 0.6BaAl2Si2O8−0.4CaSnSiO5 ceramic. The sintering temperature of 0.6BaAl2Si2O8−0.4CaSnSiO5 ceramic decreased from 1375°C to 950°C by introducing 2 wt.% LiF. The 0.6BaAl2Si2O8−0.4CaSnSiO5−2 wt% LiF ceramic exhibited remarkable microwave dielectric properties (εr = 7.6, Q × f = 17 420 GHz, and τf = −12.2 ppm/°C) and could be applied to the low‐temperature co‐fired ceramic (LTCC) field.