The present invention provides the buffered aqueous preparation of Avastin. The preparation includes citrate phosphate buffer agent and polysorbate 20 comprising trehalose or sucrose. The preparation has about 5.8 to about 6.0 acid pH, and improve the conformation and colloidal stability of Avastin molecule. The level of reduction reversible aggregation body and covalent dimer is low in the citrate phosphate buffer agent, and this buffer further provides for the protection of anti-storage stress, but not any critical biophysical descriptor of modifications or changes antibody.
