In this work, we study a multi-source enabled wireless power transfer (WPT) network. Activated by the en-ergy harvesting (EH), short packet transmissions from multiple sensors are operated via finite blocklength (FBL) codes. For such a multi-source WPT network, for the first time we characterize the overall FBL reliability and correspondingly provide a reliability-oriented design, while a practical nonlinear EH model is con-sidered. In particular, we investigate the relationship between the overall FBL reliability and the assigned power levels at multiple WPT sources. In addition, a power allocation problem is formulated aiming at minimizing the overall error probability under a total power constraint at the WPT sources. To solve the non-convex problem and specifically to tackle the difficulty introduced by the nonlinear EH model, we apply successive convex approximation (SCA) method, and conduct a set of convex approximations to the problem, with which an efficient solution is achieved via an iterative algorithm. Finally, by the means of simulations we validate our analytical model and evaluate the system performance.