The invention belongs to the technical field of Web service composition in the service computing paradigm, and discloses a method for excavating WS-CDL choreography parallelism based on the PETRI net. The method for excavating WS-CDL choreography parallelism based on the PETRI net is carried out according to the following steps: step 1, WS-CDL choreography is used as an input file, the PETRI net is used to describe the WS-CDL choreography, and the WS-CDL choreography is converted to choreography defined based on the PETRI net; step 2, from the point trace equivalence, whether the choreography defined based on the PETRI net and the WS-CDL choreography satisfy the trace equivalence is examined, if the choreography defined based on the PETRI net and the WS-CDL choreography do not satisfy the trace equivalence, the conversion in the step 1 is considered to be unsuccessful, the step 1 is returned, and the PETRI net generated by the conversion process is modified; if the choreography defined based on the PETRI net and the WS-CDL choreography satisfy the trace equivalence, the conversion in the step 1 is considered to be successful, and a step 3 can be carried out; step 2, control flow relation and interaction relation of the choreography defined based on the PETRI net are analyzed, the dependence relationship is calculated, and a dependence graph is constructed in order to search possible parallelism and interaction in the choreography.