Ammonium dihydrogen phosphate (ADP) is a pioneer kind of nonlinear optical crystal. It can be used in various electro-optical, nonlinear optical applications. The pure and different weight percentage of Picric acid doped ADP single crystals are grown using the slow solvent evaporation technique at room temperature. The powder XRD study shows single phasic nature of all the grown crystals. The photoluminescence study suggests that the dopant causes defect in structure of ADP by virtue of vibration relaxation and self trapping exciton. The dielectric constant and the dielectric loss of all the grown crystals exhibited universal behaviour over frequency range considered. The Correlation Barrier Hopping and the Non Overlapping Small Polaron Tunnelling kind of conductivity mechanism are observed. The grain and grain boundary is indentified using the complex Impedance and the complex modulus spectroscopy. The third order nonlinear optical susceptibility is increased on doping the Picric acid in ADP crystals. The results are discussed here. © 2020 The Physical Society of the Republic of China (Taiwan)