African swine fever (ASF) is a devastating disease of pigs caused by African swine fever virus (ASFV), which is considered to be the No. 1 killer to the global pig industry. Highly virulent strains are usually responsible for the peracute and acute forms that provoke high mortality rates that may reach 100%. Since ASF was first introduced in August 2018 into China, 137 outbreaks in domestic and wild pigs had been reported from 32 provinces by June 06, 2019, causing severe socioeconomic consequences. Efforts to develop an ASFV vaccine began in the 1960s, but all failed, the major reason is the lack of in-depth research on the biological characteristics of ASFV. It will be a great challenge for China to control the spread of current ASF, develop safe and effective vaccines. In this review, we outline the biological characteristics of ASFV, including its morphology and basic structure, transmission routes, pathogenicity, genome and proteins, entry mechanism, immune escape, and analyzed the difficulties in vaccine development. We hope to provide basic information for the control of current ASF and understanding of etiology in China.