The accurate determination and estimation of grain moisture content is important for maize (Zea Mays L.) production, processing and drying studies. However, different drying procedures are often adopted by different operators to determine the grain moisture content, making it difficult to compare results with each other. In this study, different drying temperatures and times were used to create different drying conditions, and the differences in the estimated grain moisture content of maize were analysed. The results showed that, compared to the standard system, an insufficient drying temperature and time contributed to a lower apparent moisture content of maize grain, but the low drying temperature could be compensated by a longer drying time, and vice versa. Additionally, a correction method for maize grain moisture content was built. This method can correct the apparent moisture content (nonstandard system) under different drying procedures to the specified standard system, and the accuracy of model validation and the stability of deviation are very satisfactory. This method is very suitable for the rapid conversion of the grain moisture content of maize between different drying methods. It is especially helpful for re-evaluating the differences and controversies of some conclusions caused by different drying procedures adopted by different researchers, and provides a reference method for moisture content correction of other foods and cereals.