For the precise ammonia (NH3) measurement, an ammonia measurement technique using femtosecond laser filament-triggered discharge is proposed. Discharge is triggered by long filaments formed in air by femtosecond laser pulses. The plasma emission spectra of NH3 under different conditions were obtained by using a spectral acquisition system. The calibration curve for NH3 concentration was obtained by utilizing the ratio of peak areas of characteristic spectral lines in the emission spectra. The one-dimensional spatial distribution of spectral line intensity was analyzed. Experimental results demonstrate that the ratio of characteristic spectral line peak areas exhibits excellent linear response to NH3 concentration. The one-dimensional spatial distribution of characteristic spectral line intensities exhibits good stability. Femtosecond laser filament-triggered discharge for NH3 concentration measurement enables real-time quantitative NH3 detection with one-dimensional measurement capability. This technique provides a novel approach for real-time in situ measurement of NH3.