Abstract: This article analyzed the influence an contribution of the illegal land use investment between 1999 and 2006 in China based on the mechanism that the land use investment illegal to economic growth. The study shows that illegal land investment may have a different effect from that of legal land investment because of different gaining ways and so on. In a short time, illegal land investment has a smaller output elasticity than that of legal land investment. And looking for a long time , the illegal land investment does harm to land use intensity and may make a negative effect on economy growth. All in all, the government should try their best to impediment illegal land use with various measurements.