The invention relates to a method for vertically processing a cooling passage of a liquid rocket engine thrust jet, which belongs to the processing method field of liquid rocket engine thrust jet. In the invention, the thrust jet adopts a vertical clamp; a single-point laser sensor scans bus bars strip by strip to acquire the actual profile of the thrust jet and a sampled data set to reconstruct the bus bars of the thrust jet strip by strip; the buses of the sampled data set are smoothed strip by strip to acquire a thrust jet smoothed data set; the data set of all the bus bars are compressed to acquire a compressed data set; and a cubic spline is used for performing interpolation to approximate the actual bus bars of the thrust jet. The milling tool position is calculated by dual milling head for symmetrical milling and high speed back chipping. The method realizes the integration of measurement and processing, finishes the treatments of profile measurement, milling groove and back chipping by one clamping, can satisfy the processing requirements on different physical dimensions and different bus bar linetypes, has high processing efficiency and good consistency, and realizes the digital processing with high efficiency and high precision of the cooling passage of the liquid rocket engine thrust jet.