We need to develop a low energy consumption, green and environmentally friendly process for preparing double perovskite fluorescent powders, and incorporate other metal ions into the matrix to obtain a new type of luminescent material with high quantum efficiency. In this study a microwave solid-state method is used to prepare Bi³⁺ doped lead-free double perovskite Cs₂Ag_0.6Na_0.4InCl₆ fluorescent powders. This method does not require ligand assistance and is environmentally friendly. The crystal structure and morphology are characterized by X-ray diffraction and scanning electron microscopy, and the luminescence performance is studied by excitation spectroscopy, emission spectroscopy, time-resolved spectroscopy, and quantum efficiency. The results are shown below 1) The Cs₂Ag_0.6Na_0.4InCl₆ is a cubic crystal belonging to the Fm\bar 3 m space group, and its grain morphology is irregular. 2) When the optimal doping concentration of Bi³⁺ is 0.0013 mmol, the emission center wavelength of Cs₂Ag_0.6Na_0.4InCl₆ material is 562 nm, the average fluorescence lifetime reaches 2.60 μs, and the quantum efficiency attains 45.28%. 3) When the concentration of Bi³⁺ ions exceeds 0.0013 mmol, a significant concentration quenching effect occurs, which is mainly due to the electric quadrupole electric quadrupole (q-q) interaction between Bi³⁺ ions. 4) The chromaticity coordinates of the Cs₂Ag_0.6Na_0.4InCl₆ doped Bi³⁺phosphor are located in the yellow-light region, making it a potential yellow phosphor for warm white light emitting diode (LED) applications.