A defect chemical model for the behaviour of acceptor-doped LaCrO3 as a function of oxygen pressure is proposed. This is considered within the regime that corresponds to oxygen deficit oxygen. The mathematical approach allows us to calculate the oxygen partial pressure dependant properties of LaCr1-xMgxO3- in the value(x= 0.05, 0.1, 0.2). The results show that the conductivity was independent of pO2 and was proportional to the dopant concentration at high pO2. Therefore, under reducing conditions, the conductivity decreased exponentially with decreasing pO2 and asymptotically approached a pO2 1/4 relationship Stability regimes and compensation mechanisms at various oxygen partial pressures and temperatures are proposed. This model also examines the charge compensation mechanisms that dominate under the different regimes and their implications for transport properties. From equilibrium constants, thermodynamic quantities such as standard enthalpy and entropy change for the defect formation reactions were calculated.