A method was established for the quantitative analysis of protein based on electrospray-differential electromigration-particle counting.Effects of factors such as electrospray voltage,liquid solution flow rate and gas flow rate on particle size distribution were systematically investigated and optimized,and common silica capillaries with an inner diameter of 25 μm and a length of 4.07 cm were used.The method was applied to the quantitative analysis of bovine serum albumin reference materials.Results showed that,under the condition of Taylor cone,a bovine serum albumin reference material and a bovine serum albumin solution reference material could both be accurately quantified at a sample solution flow rate of 300 nL/min,an air flow rate of 1.0 L/min and a carbon dioxide flow rate of 0.1 L/min,with the determined results of 20.05 g/L and 69.52 g/L,respectively.The relative errors were within ±5%,which were consistent with the quantitative values of standard materials.With no need of internal and external standards,the method is fast,accurate and sensitive,and it provides a new analytical approach for absolute protein quantification.