The practice of oil and gas exploration shows that the metamorphic mudstones (slates and hornfels) can be profitable hydrocarbon plays when their petrophysical properties are transformed by igneous intrusion. Meanwhile, igneous intrusions surely effect sandstone country rocks by providing hydrothermal fluids and causing hydrothermal convection. It has great significance to explore the influencing factors and mechanism of intrusive body to country rocks as it is an important aspect to take account in reservoir evaluation and expanding hydrocarbon exploring regime. From this perspective, this paper generally summarizes the intruding and influencing process, the relationship between intrusive activities and hydrocarbon reservoirs, and the major study progresses. From standpoint of reservoir properties (porosity and permeability) and author’s case studies, the influencing factors of intrusion to country rocks are concluded as following aspects. They are: ①pressing deformation mechanism. This mechanism includes plastic deformation or brittle fracturing in macroscopy, detrital grain fracturing and pressure dissolution in microscopy. ②heat transferring and hydrothermal metamorphism. Sandstone country rocks are transformed by hydrothermal convection. Thermal metamorphism of mudstone occurs due to heat baking. Metamorphic geological structures are formed. ③intruding activities provide material sources for diagenesis directly and indirectly, causing dissolution or precipitation. These influencing factors have double effects on country rocks. On the basis of thorough discussion and conclusion above, further studies are proposed in this paper. Hydrothermal convection mechanism study, determining intrusion's influencing range, studying influencing mechanism of different intruding conditions and intrusion characteristics and establishing corresponding models are the main focus for further exploration of influencing mechanisms of igneous intrusions.