Abstarct: Recently, production of complex industrial products from mextallic tubes with purpose of high strength to weight ratio specially in reduction of fuel consumption of transportation devices have been focused by researchers. In this case, tube hydroforming is a novel applicable method. Tearing in forming of sheet and tube mextals is considered as a restricting phenomenon that is evaluated by forming limit diagram (FLD). Using FLD of conventional forming process is not appropriate for hydroforming process. Also, FLD of sheet forming process is not proper for tube hydroforming process. In the current work, with the aim of empirical prediction of FLD of 304 stainless steel, firstly numerical investigation of hydro bulging process with various load path and die geometry has been performed on strain path and plastic instability. In order to investigate effects of load path, three types of loading condition, namely free loading, loading with axial feeding and loading with fixed tube ends have been studied. Study on geometry of dies has been performed by varying die corner radius (R) and bulging length (W). Here, effect of axial feeding on strain ratio (β) has been studied. Numerical results indicated that strain path in conditions of free loading and loading with clamps end are similar and located in the right hand side of FLD. In this condition, by increasing of W, the β tends to value of zero that this situation is independent to boundary condition. By increasing of R in free loading condition, by reduction of β the strain path is approached to plane strain state; while in loading with axial feeding condition, increasing of R has neglect able effect on strain path. In loading with axial feeding condition, increase in axial feeding the β is reduced drastically. In empirical study, from the simulated tests, number of 10 tests with distributed loading path condition was selected on strain diagram. After designing and manufacturing of the dies, meshed tubes are loaded controllably until tearing and the FLDs have been drawn using strains which were obtained near tearing locations. Also, the FLD of 304 SS tubes in current work, has been compared with FLD of SS sheets in other works. At the end, in order to investigate efficiency and accuracy of developed method, it was used for forming of a tube cam type profile. Numerical and empirical results showed that obtained FLD can predict the forming of tube cam. Moreover, formability of this industrial part verified that obtained FLD of this work is appropriate for forming of other industrial parts.