The autopilot is the crucial device for a unmanned aerial vehicle to implement autonomous flights and missions. Most of the existing commercial autopilots have no hardware reinforcement, which will lead to a risk in carrying out some significant tasks. The analysis reveals that the control resolver is the module which performs the greatest impact on the security and the reliability in the composing of an autopilot. With the increasing fault-tolerance requirements, 4 reinforcements were respectively designed, namely, the single resolver reset reinforcement, the dual resolver hot backup reinforcement, and the dual host systems switched by hardware and software. Several simple devices such as repositors, counters, inverters, selectors, and additional codes inside the resolvers were used to build the reinforcements. The reliabilities varying with time of the reinforcements were emphatically studied and comparatively analyzed. With the simulation of the working mechanisms, the fault-tolerance performances, such as the abnormal output durations, of the reinforcements in fault treatments were analyzed. The calculations show that all the reinforcements can obviously enhance the reliability of the autopilot, of which the dual host systems increase the most. This research provides a meaningful direction to the tradeoff of the fault-tolerance performance, complexity, and cost in high reliability autopilot designs.