Proper prediction of Length Of Stay (LOS) has become increasingly important these years. The LOS prediction provides better services, managing hospital resources and controls their costs. In this paper , we compared two Machine Learning (ML) methods on the Microsoft available dataset. This data are been firstly preprocessed by combining data transformation, data standardization and data codification. Then, the Random Forest (RF) and the Gradient Boosting model (GB) were carried out, with a phase of hyper parameters tuning until setting optimal coefficients. Finally, the Mean Square Error (MAE), R-squared (R 2) and the Adjusted R-squared (Adjusted R 2) metrics are selected to evaluate model with parameters. The best model is saved to be trained with real data later using transfer learning techniques.