The model-based software testing method is one of the most effective ways to improve the quality and reliability of embedded real-time system software. However, general models usually lack the description of their real-time characteristics and software behavior for the reason that this type of software is complicated with the real-time characteristics. As a result, a wealth of professional domain knowledge is required to build them more accurately and completely. This gives modeling a rise in difficulty and cost. It is thus difficult to guarantee the adequacy and effectiveness of the test. The usage scenario is an example of the interaction between the user and the software, which describes the system behavior of the software in detail without paying attention to its internal complex structure. Therefore, to reduce the difficulty of modeling, this study builds the model based on the standardized representation of the usage scenario and uses the time-extended EFSM model to describe the real-time characteristics of this type of software; to ensure the integrity of the model, this study designs the evaluation criteria for model integrity to determine whether the model fully characterizes the behavior of the system by verifying the integrity of the constraints in the model transitions; for the incomplete model, a to-be-completed transition generation strategy is designed according to the constraints to generate the to-be-completed transition, and it is completed into the model through the execution process of the feasible transition sequence of the dynamic simulation model to enhance model integrity; finally, this study builds a time-extended EFSM model for four pieces ofembedded real-time system software and carries out a series of experiments. Experiments show that the method proposed in this study can not only build the model but also complement the generated to-be-completed transitions to the model, further improving model integrity.