Equine Infectious Anemia Virus (EIAV) is a retrovirus that establishes a persistentinfection in horses and ponies . The virus is characterized by acute and chronic recurringclinical signs including fever, anemia, edema and cachexia in some animals. The virus is in thesame lentivirus subgroup that includes human immunodeficiency virus (HIV). The similaritiesbetween these two viruses make the study of the immune response to EIAV make it relevant tothe research on HIV. In this paper, a modification of the homotopy perturbation method isapplied to solve a mathematical model of within-host EIAV infection dynamics which containboth humoral and cell-mediated immune. This model is a nonlinear ordinary differentialequations. Example is provided to show the ability and reliability of the method. The resultsreveal that the method is very effective and simple.