In this paper, a formal strongly consistent transformation from UML Sequence diagrams (SDs) to Queueing Petri Nets (QPNs) is defined. Sequence diagrams are charts used to identify the sequence of event occurrences of a certain audience. QPNs are graphical formalisms, at a lower level of abstraction, for which efficient and mature simulation-based solution techniques are available. We show how the language of sequence diagrams is mapped onto an equivalent language of QPNs through formal transformation rules. We develop 12 general rules for formal SD-to-QPN transformation. We also present applying the proposed rules for a typical case study of a cloud service system. Experimental results are also provided.