The invention discloses a method for preparing a low-dielectric-constant microwave dielectric ceramic material by a solid phase synthesis method, and belongs to the raw ceramic powder preparation technology in the field of low temperature co-fired ceramic (LTCC). With adopting of a conventional process and conventional equipment of the low temperature co-fired ceramic field, the ceramic powder material is prepared through the procedures of proportioning, ball milling, melting, crushing, compounding, secondary ball milling, granulating and the like. The ceramic material has the many advantages of low dielectric constant, low dielectric loss, good temperature stability, good processability, cheap raw materials, simple preparation process, low production cost, no special requirements on the equipment workshop environment and the like. The low-dielectric-constant microwave dielectric ceramic material provided by the invention can be used as a core material of electronic circuit substrates, resonators, filters, microwave substrates and microstrip lines, and also has important application prospects and economic benefits in electronic circuits, microwave communication, satellite communication and radar systems.