The Er³⁺, Yb³⁺ and Mn²⁺ co-doped perovskite NaMgF₃ submicron particles have been successfully fabricated and the related upconversion (UC) emission was investigated in this paper. The UC emission spectra confirm that the emission color of the Er³⁺ ions can be modulated by the doping of the Mn²⁺ ions, the incident laser power and the laser pulse-width. The UC emission results demonstrate that the key factor to modulate the UC emission color of the Er³⁺ ions is the Mn²⁺ ions in the submicron particles, in which the NaMgF₃ submicron particles have the largest relative green emission bands with the 3% Mn²⁺ concentration. The experimental results also confirm that the UC intensities ratio of the green to the red emission will increase with the increase of the incident laser power and the decrease of the laser pulse-width. All the UC emission results imply that there are two energy transfer paths from the Mn²⁺ state ⁴T₁ to the Er³⁺ ions, in which the transfer rate to the state ⁴S_3/2 is far larger than the transfer rate to the state ²H_11/2 and the energy transfer mechanism may related with the special structure of the Mn²⁺ ions and the phonon-assisted processes.