GB/T 6743-2008 is a Chinese national standard, which specifies the determination method of partial acid value and total acid value of polyester resin for plastics and lacquer base for Paints and varnish. The standard contains two methods: Method A is used to determine partial acid value, which is suitable for lacquer base and unsaturated polyester resin for Paints and varnish; Method B is used to determine total acid value, especially for unsaturated Resin with large free anhydride content. The standard provides detailed experimental procedures, instrument requirements and result calculation methods, aiming to provide data support for product quality control and polycondensation reaction monitoring.