In order to elevate the allowable current density of pyrophosphate bath, glycerol was employed as additive for copper electrodeposition, and its influences on cathodic current efficiency, coordination environment, electrodeposition behavior and coating properties of conventional pyrophosphate bath were systematically investigated. It was demonstrated that glycerol did not change the coating's nucleation mechanism and purity, and had almost no effect on the bath's current efficiency, but effectively improved the allowable current density, increased the cathodic over-potential, and suppressed the hydrogen evolution in copper electrodeposition processes by absorption onto electrode surface. Specially, the coating electrodeposited from this optimized bath also had lower porosity and smaller micro-strain than that of produced from conventional pyrophosphate bath. Detailed analyses were conducted to clarify the mechanism responsible for the improvements. (C) 2018 The Electrochemical Society.