Gas submerged jet penetration length is a key parameter for many industrial applications. Many experimental and theoretical works have been performed on pure steam and non-condensable gas submerged jets. However, the steam-air mixture gas submerged jets are not yet fully understood. So, a series of visualization experiments are performed to investigate the effect of air mass fraction, jetting direction, water temperature and inlet pressure on mixture gas submerged jet penetration length. Two flow regimes are distinguished based on the evolution of the interface between water and mixture gas, which are referred to as stable regime and oscillation regime. A flow regime map is developed based on inlet pressure and air mass fraction. A momentum balance model for predicting jet penetration length is proposed. Results show that the mixture gas jet penetration length increases with the increasing inlet pressure and decreases with the increasing air mass fraction. The water temperature has little effect on the jet penetration length. A new correlation for dimensionless vertical jet penetration length is developed based on the form of model analysis. The discrepancy between predicted results and present experimental data is within +/- 5%. A new correlation for dimensionless horizontal jet penetration length is developed based on experimental results. The discrepancy between predicted dimensionless horizontal jet penetration length and experimental value is within +/- 18%. (C) 2018 Elsevier Ltd. All rights reserved.