Abstract: The interaction of ultrahigh intensity laser with overdense plasma is studied using a 2.5D particle simulation code. A channel is formed due to the extremely large ponderomotive force associated with laser pulse. Strong self-generated magnetic fields produced by strong flow of high-energy electrons are observed. Three kinds of spatial profiles of laser intensity are used to investigate the effect of laser spatial profile on boring , and it is found that the boring effect is stronger when the radial gradient of laser intensity is bigger. Odd and even harmonics are found in reflected waves.