A tidal level measurement project was carried out to estimate the design criteria for enginnering applications in the Chengdao Oil Field located northwest of the Yellow River estuary. Sea level was measured at a coastal station for a period of more than one year winter excluded because of icing. In the offshore area, tidal measurements were carried out at 8 stations: at one station for 2 months, at another 3 stations for 1 month, and at the remaining 4 stations for 2 days. The tidal records from offshore stations were analysed using regular methods. The tidal record at a coastal station was often interrupted during low water period. To extract tidai harmonics from these interrupted data, data gaps were filled artificially before conducting tidal analysis to obtain the harmonics, used to predict the sea level for the poriod of the gaps. Then the predicted sea level heights were used to replace the artificially given heights and a new analysis was made. The same procedure was repeated several times until the harmonics did not change. To confirm the validity of this approach, we used the tidal retcord of the longest offshore station and discarded the low water part data. The remaining data were analysed using the above approach. The obtained tidal harmonics differed only slightly (within 0.6cm in amplitude and 2° in phase lag) from those obtained by using original complete data. Analysis of the sea level records, yielded the distribution of the sea level for use as design criteria for engineering applications in the Chengdao Oil Field.