Abstract: Stylolite structure is widely distributed in deep burial acidic volcanic rocks in the northern Songliao Basin.Macroscopeically, stylolites can be divided into two groups. One group often develops along the interfaces of different rocks or fluxion planes and its shape and dip are controlled by these interfaces. The other group is related with the tectonic fissures. The results of observation by scan electronic microscope show that the stylolites have a complex spatial shape and their column-sides are characterized by micro- striations. Analysis by electronic probe indicates that the stylolites in volcanic rocks are composed of iron oxides, kaolinite and leopoldites, partially with a small amount of carbonates. Through comprehensive analysis, a conclusion can be drawn that the stylolites in volcanic rocks developed in the post-diagenetic period and are related with the dissolution of quartz and alteration of feldspar. The generation of stylolites may be controlled by the lithologic characters, ground temperature,fluid regime and ground stress.