Decommission platforms can be used as the foundation of offshore wind turbines. In order to reduce the costs of wind power, the joint probability method is applied in the joint design of marine environmental elements. Based on copulas and univariate maximum entropy margins, multivariate maximum entropy distributions are constructed. Sample data of annual maximum significant wave height and corresponding wind speed and current velocity at Point 2 in Lianyungang Harbour of China is applied to testify the efficiency of trivariate maximum entropy distributions. The marginal fittings of univariate maximum entropy distributions and the trivariate data fitting based on normal copula fit the data well. The method of conditional probability can present a joint design of significant wave height and corresponding wind speed and current velocity. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.