In order to prepare the composites with excellent electromagnetic shielding performance and mechanical properties, the carbon fiber modified phenolic carbon foam was prepared by high temperature carbonization with phenolic resin as matrix and carbon fiber as filler. The effects of carbon fiber content on the composite cell structure, electromagnetic shielding effectiveness and mechanical properties were investigated. The results show that the carbon fiber can improve the carbon foam cell structure effectively, when the content of carbon fiber is 3wt%, the phenolic foam matrix show smallest cell size and most uniform cells distribution, the average cell diameter is 150μm. Carbon fiber can effectively improve the carbon foam electromagnetic and mechanical properties.The compressive strength and flexural strength of the composites reach 4.41 and 3.85MPa, which has increased by 60.3% and 71.8%, respectively, compared with pure carbon foam.When the carbon fiber content is 5wt%, the average electromagnetic shielding effect of the carbon foam on the frequency of 8~12GHz is 35dB. When the carbon fiber content is 3wt%, the carbon foam composites show the best mchanical properties.