Solid fuel ramjets (SFRJs) have the advantages of light weight, simple structure, high reliability, high economy efficiency etc. During the transient situation, their actual time fuel consumption can be different from the simple linear control rules due to the limit of mechanical structures. The volume effect can also be treated as an influence factor of fuel. As a result, the dynamic characteristics of fuel will influence the transient performance of SFRJs. To better understand its impact, in-house models for SFRJs' transient performance and fuel's dynamic characteristics are built and simulated. During accelerating and decelerating processes, the actual time fuel consumption has characteristics of time-lag. There will exist thrust lost or superfluous thrust. Compared with acceleration processes, the dynamic characteristics of fuel would be more influential in deceleration processes.