Energy loss straggling was found to be critical for evaluating the energy of the reactions using heavy-ion beams in the early stage of experiments at accelerator facilities. Despite significant attempts simulating this quantity using computer codes such as LISE++ and SRIM, there still exists adiscrepancy between experimental data and computed results. In this study, we provide a greatly improved precision of estimations using the LISE++ code by evaluating the energy loss straggling of the alpha particles at 5.486 MeV in Tb, Ta, and Au materials. After comparing with the observables, it was found that the ratio of the energy loss straggling computed by the LISE++ code to that measured in experiments has a fairly large range of 1.5 - 3.0. For this reason, the so-called modified LISE++ calculation is constructed by adding the adjusting parameters into the original estimation to minimize the uncertainty of the straggling prediction. The modified calculation has shown dramatic improvements in the computation of the energy loss straggling, which are almost similar to those obtained from the measurements, of 5.486-MeV alphas in the aforementioned materials with the atomic numbers in a range of Z = 65 – 79.