Broadband Terahertz(THz) source can generate a broad THz spectrum, which has been paid more and more attention in recent years. Broadband THz wave has the advantages of low energy, strong penetrability and broadband frequency, which indicates great potential applications in the fields of biological and medical imaging, security check, chemical analysis and so on. In this paper, three broadband THz sources of optical radiation source, electronics radiation source and heat radiation source are analyzed and summarized according to the mechanism of generation, research progress and future development trends. The advantages and application ranges are contrasted as well.