To obtain the effects of mass fraction of carbon black and environmental pressure on the ignition and combustion performance of polyethylene, the solid fuel samples with different composition ratio were processed, their ignition and combustion characteristics were investigated by using a CO₂ laser as the ignition source. The experimental process was recorded with a high speed camera. The surface morphology of solid fuels after combustion were examined using scanning electron microscope. The ignition and combustion processes, ignition delay time and burning rate of solid fuel samples with different composition ratio at different environment pressures were analyzed. Results show that the ignition process of solid fuel polyethylene is a typical gas phase ignition and combustion flame is a diffusion flame. The ignition delay time shortens sharply with the addition of carbon black, when the mass fraction of carbon black is higher than 20%, the effect of increase of mass fraction of carbon black on ignition delay time is very small. The ignition delay time shortens with the increase of environment pressure, when the environment pressure is higher than 0.2 MPa, the effect of increase of environment pressure on ignition delay time also is very small. According to the experimental results, when the environment pressure is 0.1, 0.2, 0.3, 0.4, 0.5 MPa, the function relationship between ignition delay time and mass fraction of carbon black is fitted and obtained by using the least squares method. The burning rate of solid fuels decreases with the increase of mass fraction of carbon black, and increases with the increase of environmental pressure. The mass fraction of carbon black is the main factor affecting the burning rate of solid fuels when the mass fraction of carbon black is higher than 5%.