For the limitation of calculating and designing the design tide level process line with the same ratio method and samefrequency methods, and based on using 4 kinds of marginal distribution functions to fit the annual highest tide level and maximumtide range sequence in the Pearl River estuary, this paper selected 4 kinds of different two-dimensional Archimedean Copula functionsto establish the joint distribution of annual highest tide level and annual maximum tide range in the Pearl River estuary, andanalyzed the linear relationship between the return period of highest tide level and simultaneous return period of tide level process.The results show that the simultaneous recurrence period of highest tide level and tide range is always more than that of marginaldistribution. Besides, with the increase of return period of marginal distribution, the simultaneous return period will also be increased,and this shows that the possibility of simultaneous return period of highest tide level and tide range is very small. In theend, the joint distribution method is more reasonable than the same frequency method in calculating the tide level process line inthe Pearl River estuary.