Abstract: The RETRAN-02 computer code developed by US EPRI is a versatile and reliable thermalhydraulic code used for best-estimate analysis of LWR systems. It was transplanted on CYBER-825 computer at CLAE in 1986 and now is applied for the safety review calculations of design basis accidents for Qinshan NPP, e. g. main steam line break, steam generator tube rupture, loss of flow accidents, reactivity accidents and anticipated transients without scram. The calculation results are an important support for safety review for Qinshan NPP.Self-consistent steady-state initialization is an advantage of RETRAN over the other computer codes of same kind (e. g. RELAP5). The paper introduces the experiences of the authors in evaluating and adjusting the steady-state Initialization and choosing the special models. As an example, the main steam line break analysis is given.