Abstract: In order to studied the change of tide rule duing to the second channel engineering at huanghua port, tidal observation precision was evaluated about tide monitoring and issuing system at huanghua port. Mean sea level and depth datum were calculated and new tide rule was re- searched. On the basis, a critically mathematical model of datum is proposed in the paper. Channel datum about different place of channel was designed for engineering application. The numerical test results have shown that the calculation, the design and the engineering application of datum at huanghua port has important signification and application value to engineering and produc- tion, and so on.