Al-PTFE (Aluminum-Polytetrafluoroethylene) is a promising composite as a kind of impact initiated energetic materials. The impact sensitivity of Al-PTFE was characterized by drop weight tests. By varying the sintering temperature, Al mass ratio and Al particle size, the sensitivity of Al-PTFE changes significantly from 25.78J to 87.34J. It was found that in general Al-PTFE specimens with higher strength tend to be more sensitive to low-speed impact. The SHPB test was carried out on the baseline Al-PTFE specimen, and the stress ignition threshold was found to be 116MPa, which is not high enough to trigger a shock-induced reaction (SIR). Moreover, multiple evidences, including the high-speed camera records, prove that crack-induced ignition mechanism, rather than SIR, dominates the ignition of Al-PTFE upon low speed impact.