2-amino-5-nitropyridinium hydrogen oxalate (2A5NPHO) was grown using slow evaporation and bulk crystal of 2A5NPHO was harvested from Assembled Temperature Reduction (ATR) method. Cut and polished crystal was irradiated using Au3+ ion with various fluences. Electronic loss, nuclear energy loss and penetration depth were calculated using SRIM software. It was observed in X- ray pattern that intensity of peak was reduced. Intensity of peak decreased with increase of ion fluencies from 10(13) ions/cm(2) to 10(14) ions/cm(2). Optical properties were measured using UV-Vis spectrometer. The increase of absorption was due to excited electrons which were formed by vacancies and formation of additional defects centres. Energy band gap of irradiated crystals increased with increase of ion fluence. Energy band gap of irradiated crystals were 3.39eV, 3.42eV, and 3.4eV for 10(13) ions/cm(2), 5 x 10(13) ions/cm(2) and 10(14) ions/cm(2) respectively and increase of band gap was due to the increase of forbidden gap. Microhardness was calculated using Vicker's Hardness tester. Increase of microhardness in irradiation crystal was due to increase of high density lattice defects produced by Au3+ of 10.8MeV. Electrical property was calculated using dielectric constant. Increase of dielectric constant was due to large polarization which caused by disorderness and rich defects in the crystalline surface. Decrease of intensity peak in fluorescence was due to transition of excited electron to intermediated energy levels from excited state which converted into vibrational energy of lattice atoms (phonon). Morphology of irradiated crystal was seen using scanning electron microscope (SEM). It was observed from the SEM image that surface of crystal was heavily damaged. It was also noticed that the thermal stability of the irradiated single crystal increased with increase of ion fluences. Impedance of irradiated crystal was measured. The bulk resistance and grain boundary resistance also were calculated.