The paper reports the comparative studies on the laser-induced single-shot and multiple-shot surface damage thresholds of nonlinear crystals, viz. Urea, 3-methyl-3-nitropyridine-1 oxide (POM), L-arginine phosphate (LAP) and beta-barium berate (BBO) crystals. The measurements were made using radiation of 1064 nm and its second harmonic generation, i.e. 532 nm from a Q-switched Nd:YAG laser of pulse width 10 ns. In addition, the effect of Na+ impurity incorporated during growth in BBO crystal in different concentration (wt.%) has also been studied, and attempted to be correlated with various factors. We also measured the absorption coefficients of these crystals at different wavelengths. The Scanning Electron Microscope coupled with Energy Dispersive X-Ray Analyzer (SEM-EDX) has been employed to study the inclusions/impurities present in the crystals.