Abstract: A code was developed to predict the leakage from through pipeline crack of the leak before break (LBB), and various stagnation conditions were considered, including the subcooled water, the two-phase fluid and the superheated steam. Both the critical and non-critical flows were studied. The Henry-Fauske critical flow model was revised by a new phase transition point and the pressure drops of friction and turns were modified. The code was verified by comparing with the experimental data of conventional straight pipe, artificial crack and naturally occurring crack, which shows a good agreement and the code has a higher precision than the existing codes PICEP and SQUIRT. The influence of crack morphology on LBB leakage was discussed, including the local roughness, the global roughness, the crack open displacement and the number of the corners. Besides, the dependence of the LBB leakage on stagnation enthalpy and back pressure was investigated.