A new organic SHG active salt 3-Nitroanilinium L-tartrate m-nitroaniline (MLM) was synthesized and optically good single crystals were grown by solvent evaporation solution growth method at room temperature. The structure of the crystal identified by single crystal XRD analyses and it belongs to monoclinic crystal system with polar space group P21. The functional groups present in product have been confirmed from the FT-IR spectral study. The optical transmission spectrum was recorded to examine the optical property of the title crystal. The thermo gravimetric and differential thermal analyses were carried out simultaneously to study the thermal behavior of the title crystal. The relative second harmonic generation activity of the title crystal was confirmed by the modified Kurtz-Perry powder test and it was found that the title crystal has 0.5 times second harmonic generation output than that of KDP.