Natural ventilation design strategy was an important means to effectively reduce energy consumption and improve indoor air quality. The indoor temperature prediction methods could be well described the natural ventilation effect in the early design stage. Building thermal mass was the main influence factor of indoor temperature prediction of nature ventilation building through the literature review. The current simulation methods were difficult to achieve quick and accurate prediction coupled with building thermal mass. Therefore, most of the prediction methods were numerical solutions methods or prediction methods based on historical data. In order to obtain a feasible method for predicting the indoor temperature of natural ventilation building, this study put forward a simplified method based on the existing prediction methods. This study was verified by the experimental platforms with light and middle building thermal mass. The results showed that the maximum errors were about 1.5 °C between the measured values and simulated values.