Abstract: The first cycled steam huff and puff test-well A1 in Bohai Oilfield appeared the difficulties of injection capacity limitation and high thermal loses. The steam dryness in bottom well didn't reach the expectation, which affected the thermal recovery effect. In order to reduce the steam injection pressure and improve the effect of steam stimulation, the orthogonal experimental method was applied to analyze the reasons of high steam injection pressure in test-well A1. The results indicated that the sensitive factors influencing the well A1 high injection pressure were successively stratum energy, formation permeability and oil viscosity. To improve the effect of steam injection, cold mining or the pre-treatment measures of viscosity reduction and injection enhancement should be taken before steam injection to reduce the formation energy. The research results can provide guidance for the subsequent thermal implementation in this block and the development of similar oilfields.