In order to study the liquid oxygen chill down process of the pipeline-injector component located downstream of the main valve of a liquid rocket engine, it was simplified to an exit-contracted pipe and two groups of experiments were conducted with high mass flux (3 750 kg.m-2.s-1) and low mass flux (1 800 kg.m-2.s-1), respectively. Based on the experimental data, flow pattern development diagrams of the fluid in the pipe were plotted and analyzed during the chill down process. Moreover, the heat transfer coefficients at Leidenfrost points (hLFP) were fitted. The detailed conclusions are presented as follows. There are three liquid rewetting patterns in the pipe during the chill down process including Ⅰ, Ⅱ, and Ⅲ, which are controlled by the quenching fronts at the inlet and the outlet, the quenching fronts in the middle, and the high pressure filling-in of the liquid, respectively. While the rewetting patterns at the front 1/4 of the pipe are always I for the experimental conditions, the rewetting patterns at the other sections of the pipe change with increasing pressure. For the middle and the rear sections, when the pressure is lower than 1.181 MPa, the rewetting patterns are Ⅰ or Ⅱ. And when the pressure is equal to or higher than 1.181 MPa, the rewetting patterns of these sections transform into I at low mass flux and Ⅲ at high mass flux. With an error of less than 34.2%,certain semi empirical formula is employed to predict the hLFP for 4 measurement points at the 0.15 m and 0.30 m cross-sections.