Mn⁴⁺, Cr³⁺ single-doped and Mn⁴⁺, Cr³⁺ co-doped BaMgAl₁₀O₁₇ phosphors were synthesized via a conventional high-temperature solid-state reaction method. Both Mn⁴⁺ and Cr³⁺ ions show broad excitation band extending from ultraviolet to visible light range, and the emission band peaks at 660 nm for Mn⁴⁺ ion and at 694 nm for Cr³⁺ ion. The relative intensity of the luminescence of Mn⁴⁺ and Cr³⁺ can be adjusted by changing the co-doped Cr³⁺ or Mn⁴⁺ concentration in the Mn⁴⁺, Cr³⁺ co-doped BaMgAl₁₀O₁₇ phosphor to better match the required light for photosynthesis of different plants. Moreover, the specific relationship between the luminous intensity ratio of Mn⁴⁺ and Cr³⁺ and the excitation wavelength in the region of 320 to 530 nm in the co-doped phosphor suggests that the excitation wavelength can be known by measuring the emission integral intensity ratio between Mn⁴⁺ and Cr³⁺. The results show that the Mn⁴⁺, Cr³⁺ co-doped BaMgAl₁₀O₁₇ phosphors can not only be used as plant growth spectral converter, but also wavelength detector.