For the real evaluation of the bubble energy and the accurate calculation of bubble oscillation period of underwater explosion, according to the existing research payoffs of underwater explosion and the similarity law, a method of accurately estimating the bubble oscillation period of underwater explosion was presented. The formula estimating the bubble oscillation period of TNT explosive was obtained via three calibration experiments of TNT explosion in sea, and the error of calculated and the experimental one is smaller than -1.34%. The formula estimating the bubble oscillation period of Al/RDX/TNTT explosive was obtained via three calibration experiments of Al/RDX/TNTT explosion in sea, and the error of calculated and the experimental one is smaller than 1.45%. The bubble oscillation period is proportional to the 1/3 powers of explosive equivalent and is inversely proportional to the 5/6 powers of summation of the converted water depth of atmospheric pressure and water depth over explosion. The bubble oscillation period is badly affected by the types of explosives. The chemical characteristics of explosive and formulas used to calculate the bubble oscillation period have strong correlation. Use of calibration method in sea can accurately estimate the bubble oscillation period of underwater explosion. The error of the estimated value and the experimented one is smaller than 2.54%. The method is suitable for estimation of the bubble oscillation period value of underwater explosion of explosive.