Abstract: With the equivalent axial force (S₀) and the interaction between the suspened pipeline and buried pipeline considered, the characteristic equation for calculating natural frequencies of the aerial crossing pipeline buried at both ends is derived. After frequency" estimation formulae in previous literatures are appraised, a new one is developed. Calculation results show that S₀ resulting primarily from the internal pressure and the temperature difference has a great influence on natural frequencies, and that the frequencies of aerial crossing pipelines are greatly decreased with the anchors cancelled out at both ends. Based on the calculation values from the characteristic equation, investigations on reliabilities of the estimation formulae arrive at conclusions that when So is equal to zero or tensile, estimation formulae give a fair accuracy; when S₀ is compressive, they give a poor accuracy, and therefore the characteristic equation should be used for frequency calculation.