Due to the lack of empirical studies of scale variables and distance exponents, the effective application of the gravity model in urban study is challenging. With the development of multi-centralized Chinese cities, the gravity model must be validated because several relevant external conditions have changed. The purpose of this study is to validate Huff's Gravity Model using an individual mobile trajectory of mobile communication user in 2015. We follow Huff's two-step validation method: variable validation and parameter correction. Our main conclusions are as follows. First, attractions of commercial and employment centres conform to the law of the gravity model in which the attraction is proportional to the scale of a centre and inversely proportional to the distance from a centre. Second, in the spatial scale of Shanghai central city with spatial units in a 200-m grid, the mean distance exponent for commercial centres is 2.5 and that for employment centres is 3.0. The distance decay for commuting is greater than that for shopping trips, which means commuting is more sensitive to distance. Third, the gravity model can be used to predict the influence areas of adjusted commercial and employment centres based on validated variables and corrected parameters. Our results indicate that the prediction accuracies can reach 78.5% and 71.9% for the commercial and employment centres, respectively. The prediction accuracy for employment centres is slightly lower. This is because the attraction of employment centres is influenced not only by distance but also by factors such as family and housing prices, which will affect the prediction results. Lastly, in this study, we verify the spatial stratified heterogeneity of distance decay and determine that the distance exponent is not a unique constant because it has different values in different areas. Factors such as accessibility, distance to each centre, distance to a subway station and population density will affect distance decay.