The invention provides a separation type catalytic bed and an engine propelling method. The separation type catalytic bed is composed of an injector, a decomposition chamber, a front bed separating plate assembly and a rear bed separating plate assembly. The injector forms a liquid propellant flow channel, and the decomposition chamber is divided into different unit decomposition regions along theradial direction of the catalytic bed. The liquid propellant is uniformly sprayed into the corresponding region of the catalytic bed through two circles of single-component nozzles, and after the catalyst is decomposed by each region, part of the fuel gas is mixed by a porous separation device and then continues to be decomposed, then enters into the independent decomposition regions of the rearbed to form secondary mixing decomposition, is subjected to three-time mixing decomposition through the porous separation device of the rear bed in the rear bed, finally the high-temperature high-pressure fuel gas formed after multiple times of interaction and mixing is discharged, so that a pushing force is generated. According to the separation type catalytic bed, anhydrous hydrazine is used asa propellant, so that the problem of long-service-life working reliability of a large-thrust hydrazine decomposition engine is solved, and high performance, long service life and steady state/pulse dual-mode work and the like are obtained.