Innate immunity and adaptive immunity are two major immune responses against pathogens. Innate immunity is responsible for the immediate immune response to pathogens. Pattern-recognition receptors (PRRs) play an important role in innate immune response. PRRs recognize regular patterns of molecule structure known as pathogen-associated molecular patterns (PAMPs). Among the PRRs, Toll-like receptors (TLRs), RIG-I-like receptors (RLRs), and DNA-dependent activator of interferon regulatory factors (DAI) display key roles in response to viral infections. This article reviews how viral infections activate PRR-PAMP signal pathways and how viruses evade immune responses elicited by PRR signal pathways.