On the Debao platform margin, writers firstly discover numerous multi phased limestone dikes of the Lower Carboniferous Tournaisian stage in the Devonian limestone. The shapes, sedimentary characteristics, age and distribution pattern of the dikes are made clear. Writers have found many conodonts of Early Carboniferous as well as the phenomena that Gnathodus and Siphnodella mixed in sedimentary dikes. Writers get a new understanding for the genesis of the dikes. The dykes are the incorporation products of tectonic movements and earthquakes. In Early Carboniferous, the Upper Devonian solidified limestones splited when the platform uplifted and settled down by the earthquake, formed deep tensile cracks, thus the Early Carboniferous soft sediments and fragments injected into the cracks, formed the dikes. Multiphased tectonic movements and tension, result in the tensile fractures repeatedly opening, lead to formation of the multiphased vertical dikes. This genesis pattern can reasonablly explain the seismic liquefied veins appear in the dikes and the dynamic factors of such deepseated dikes as well as the sources of the deepwater facies sediments and bioclastics in the dikes on a platform margin. It is important for understanding the tectonic evolution of the Youjiang basin to investigate and study the limestone dikes.