•Obtain deformation failure mechanisms of deep broken rock roadways based on a detail field investigation.•Analyze and evaluate the shortcomings of a primary support scheme using FLAC3D and onsite experiments.•Propose and validate an improved support method for roadways in broken rock mass and high geo-stress. The roadway support has always been a difficult problem in the mining engineering, especially in the deep soft rock roadway, whether it can provide endurable and effective support directly affects the safety production and sustainable development of the mine. In order to solve the supporting issues, it is necessary to make the deformation failure mechanism of deep soft rock roadway clear. This paper describes a case study of the deformation failure mechanism and support technology of deep roadway with soft rock mass in No.2 mine zone of Jinchuan mine that is located in Gansu Province, China. Based on a detailed field investigation and previous research experience, the modes, influencing factors, laws and mechanisms of deformation failure in the roadway are summarized. Then the primary combined supporting scheme “double layer bolt-mesh-shotcrete and U-shaped steel” is evaluated through numerical simulation calculation and onsite experiments. To make up for the shortcomings of the primary support, an improved combined supporting scheme “double layer long bolt-mesh-shotcrete and CFST (concrete filled steel tube)” is proposed. The results of numerical simulation, field monitoring and economic analysis show that the new support can control the deformation of the roadway effectively and has a high cost performance. Finally, several suggestions for supporting in deep soft rock roadway are put forward, aiming at serve as a reference for other engineering.