Abstract:pH value plays an important role in preparing nanoparticles using antisolvent procedure. In this research, vinorelbine tartrate loaded bovine serum albumin nanoparticles were prepared at different pH values. The preparation process of nanoparticles was analyzed in the view of potential coupling. The results indicated that vinorelbine tartrate and bovine serum albumin took the opposite charges at pH value from 4.5-7.5. However, they took the same charge at pH 2.5, 3.5, 8.5 and 9.5. Especially, vinorelbine tartrate and bovine serum albumin took +4.48 and -8.52 mV respectively. The particle size of vinorelbine tartrate loaded bovine serum albumin nanoparticles reached 193.3 nm and zeta potential reached -30.86 mV in this condition. Moreover, the preparation process of nanoparticles were optimized at this pH value and the drug loading and encapsulation efficiency of this drug were approximately up to 45.6% and 90.6%, respectively.