An extensive study was carried out to compare different models and a new approach for measuring the alpha-particle range in the CR-39 detector . The CR-39 samples were exposed perpendicularly to alpha- particles with energies ranging from 2.5 MeV emitted fro 241Am. The CR-39 samples were etched in 7.25 N NaOH at (70±0.5) °C for different durations. Both the track diameters and the track cone lengths were measured under an optical microscope. The new approach is based on measurement of the track etch rate along the particle’s trajectory as a function of the removal thickness (h) . A correlation was found to exist between the removal thickness at the maximum track etch rate (VTmax) and the range of alpha-particles in the CR-39 detector. The track etch rate data were fitted using the function VT(h) =a1 + [a2 – a3h]exp[a4h]. The ranges of alpha particles were determined by settings the first order derivative of the fittings function equal to zero, where h is equal to the range of the alpha particles (R) in the CR-39 detector . Furthermore, the range of the alpha particle in the CR-39 detector was measured using the over-etched track diameter and the track cone length. The theoretical predictions of the alpha-particle ranges were calculated using the SRIM software. A well-known function ,R( E ) =b1Eb2 , was used to fit the experimental results and the theoretical predictions. Experiments showed that the determination of the alpha-particle range based on the cone length model was in a good agreement with the theoretical calculations, where the discrepancy was less than that for the over-etched track diameter and the maximum track etch rate models.