Abstract: This paper revealed the 2-D crustal velocity structure and interface morphology by inversion of the 2-D ray tracing method along the survey line HX9 conducted by onshore-offshore seismic experiment using the large volume air-gun source in Taiwan Strait, preliminary ascertaining the deep crustal structures of the sea-land transition zone between Fujian land and Taiwan Strait. The results show that there are two velocity discontinuities in the earth’s crust, i.e., C and Moho interfaces. C interface, as a demarcation between the upper crust and lower crust, is a small velocity discontinuity, with the velocity rang-ing 0.08--0.16 km/s; whereas for the Moho interface at the bottom of crust, there is a large velocity difference being 1.02--1.29 km/s. The velocity above the Moho interface is 6.75--6.97 km/s, and that beneath the Moho interface is 8.00--8.07 km/s. Along the profile, the overall crustal interface morphology is less volatile. The thickness and its variation tendency in the upper crust are similar to those lower crust of continental area. However, the crustal interface has slightly tilted trends from land to sea, suggesting the characteristic of thinned continental crust. The Moho interface is about 31.6 km deep in the continental area， and gradually thins to about 27.4 km in the southeast coast of Fujian.