Abstract: Sequential Resource Allocation Systems with Multiple Resource Acquisitions and Flexible Routings(C/D-RAS) arc a kind of common system with higher complexity. The liveness problems of two C/D-RAS were investigated in this paper. The Petri net models of the two C/D-RAS were defined as the marked S' PGRz nets pair, which is denotedby ((N1,M01)，(N2，M02)).With the help of the resource conversation attribute of the marked S3 PGRz nets and a sufficicnt and necessary condition of transition enabling, it was proved that the legal firing sequences of transitions in(N1，M01)and(N2,M02)are consistent As a result, the final conclusion tells us that(N1,M01)is live, if and only if(N2,M02)is live. Finally,the potential application of the conclusion was briefly introduced.

Key words: Petri net, Resource allocation systems, Liveness