The Advanced Mo-based Rare process Experiment (AMoRE) is a search for neutrinoless double beta decay of 100Mo in calcium molybdate (CaMoO4) crystals by using cryogenic detectors at a temperature range of tens of millikelvin. The crystals are made of Molybdenum enriched on 100Mo (≥95%) and Calcium depleted on 48Ca isotopes (≤0.002%). The ongoing pilot experiment at the YangYang underground laboratory consists of a number of commissioning runs using six 40Ca100MoO4 crystals of a total mass 1.9 kg. At the same time, the fist phase of the AMoRE experiment with about 5 kg of CaMoO4 crystals is in preparation. The physics data of the AMoRE-pilot were analyzed and fitted with Monte Carlo simulation results to identify their background sources. In this presentation, the fit results will be presented and discussed.