We employed ab-initio calculations to investigate the structural and thermodynamic properties of Massicot or orthorhombic phase of PbO namedβ-PbO using the projector augmented-wave (PAW) method within the generalized gradient approximation (GGA).The temperature and pressure dependence of bulk modulus,heat capacity at constant pressure and constant volume,entropy,thermal expansion coefficient and Grüneisen parameter were discussed.Accuracy of two different models,the Debye and Debye-Grüneisen which are based on the quasi-harmonic approximation (QHA) for producing thermodynamic properties of material were compared.According to calculation results,these two models can be used to designate thermodynamic properties for β-PbO with sensible accuracy over a wide range of temperatures and pressures,and our work on the properties of this structure will be useful for more deeply understanding various properties of this structure.