Ritonavir, a widely prescribed antiretroviral drug, belongs to BCS class II and due to its poor water solubility, its oral bioavailability is low. The present focuses on the Formulation development and in vitro evaluation of the Ritonavir Nanosuspension by using antisolvent precipitation-ultrasonication method. for the formulation of the nanosuspension suitable polymer concentration and solvent and anti-solvent, string time and sonication time was selected based on the preliminary studies, the optimized formulation was selected based on the mean particle size was 287.3 nM, and the PDI was 0.385. The zeta potential was noticed 26.75 ± 3.25 mV, The dissolution data of the optimized formulation was done and studies shows release rate at 120 min shows at 98.2 %. The Accelerated stability studies shows that Mean particle size (nM) ranging from 241.1 to 282 nM , Saturation solubility (µg/ml) ranging from 107.85 to 111.85, CPR at 2 min (% w/w) ranging from 94.12 to 97.90 and Drug content (%w/w) ranging 98.52 to 102.12 respectively. From the regression values, it was determined that the optimized formulation exhibits zero-order drug release. The determined n value of 0.84 indicates that drug release is characterized by non-Fickian transport.