Heavy reduction technology for continuous casting was an effective mean to reduce central segregation, shrinkage cavity and improve density of large section slab. However, the rationality of pressure position directly affected the application effect of heavy reduction technology. ES355 extra-thick slab with a section of 420 mm×2 390 mm was used as the research object to establish a three-dimensional finite element analysis model of temperature field. The reliability of the model was verified by field measurement and solidification end point test of nail shooting experiment. The effects of superheat, drawing speed and specific water on temperature field and solid phase ratio in ES355 solidification process were studied by using the model. The results show that compared with superheat and secondary cooling water, drawing speed has a great influence on the temperature field, solidification end point and solid phase ratio of ES355 casting billet.