This paper examines the effects of temperature and humidity on the absorption spectrum and concentration of nitrous oxide (${\mathrm{N}}_2\mathrm{O}$) using a compact, portable open optical-path gas detection sensor system. We obtained the absorption coefficient and widened the linear function of the ${\mathrm{N}}_2\mathrm{O}$ absorption spectrum related to temperature by theoretical analysis and the high-resolution transmission molecular absorption database (HITRAN). Afterward, we conducted real-time monitoring of ${\mathrm{N}}_2\mathrm{O}$ in both campus and laboratory environments using lasers for a duration of 32 h and 6 h, respectively, and the results were compared and analyzed with the theoretical derivation. The results show that the concentration of ${\mathrm{N}}_2\mathrm{O}$ increased with increasing environmental temperature but decreased with increasing humidity. Furthermore, the variations in temperature and humidity significantly affected the peak values of the second-harmonic (2f) and first-harmonic (1f) signals. Finally, the temperature ${\mathrm{N}}_2\mathrm{O}$ concentration and humidity ${\mathrm{N}}_2\mathrm{O}$ curves were calibrated separately, and temperature changes were positively correlated with the ${\mathrm{N}}_2\mathrm{O}$ concentration, while humidity changes were negatively correlated with the ${\mathrm{N}}_2\mathrm{O}$ concentration. The experimental results indicate that the concentration of ${\mathrm{N}}_2\mathrm{O}$ and its absorption spectra are influenced by humidity and temperature, which has a significant reference value in the absorption and measurement of ${\mathrm{N}}_2\mathrm{O}$ in practical applications.