Abstract: Extreme sea statistics and combinations of environmental events or response for structures are very important problem in performance evaluation and design of coastal and offshore structures.A probabilistic method is developed that leads to the combination of typho on (hurricane) or winter storm induces winds,waves,currents and surge for a generic site.The traditional recommendation for the fixed structures is a combination of the 100 years maximum wave height with the 100 years wind and current.This approach is,however,unduly conservative,since the largest wind,wave and current values in 100 years are not expected to occur at precisely the same time.Previous studies of combinations of extreme sea environmental conditions fall into two categories:first,the generic load model defines a surface in the multivariate space of meteoro logicaloceanic variables,such as the joint probability of waves,currents,winds and storm surges; second,use of the structural response to combine the environmental variables,such as overturning moment (OTM),base shear forces and etc.While the great majority of publications are concentrated in combinations of responses,although 100 years response is not corresponding to wave,wind and current with 100 years joint probability.Since the combination design criteria is considered with extreme statistics of individual environmental events and their joint probability,in t his paper some new concept for mentioned above problems is proposed.