In spacecraft launch engineering, it is very difficult to quantify reliability of implementation process. In terms of the peculiarities which the reliability of implementation process presents, such as many sub-processes having concurrency and every sub-process having the Markovian property and homogeneity. this research presents a model of implementation processes reliability with multi-absorbing state by utilizing the model of continuous-time Markov chain (CTMC), which simplifies the state space of the implementation processes reliability through the use of bisimulation equivalence relation. Moreover, the calculation method for various state transition rates and implementation process reliability is also presented. Finally，the simulation case by engineering data verifies the role and significance of the model in the assessment schedule of spacecraft launch engineering.