The solid – state nuclear track detector (SSNTDs) CR-39 can be used to study the different factors for alpha particle. Alpha particle is very dangerous inside the human body so the study its very important. In this article, we investigated the impact of two different etching solutions (NaOH and KOH)) on registrations properties, diameter D, track Diameter growth velocity VD, number of tracks and removal layer thickness of CR-39 nuclear track detector. The two types NaOH and KOH were dissolved in water with varied normality (3,5,7,9,11)N under a temperature of (70±1)°C to create the solution. During the experiment, a source of (α-particles) with a 4MeV energy was used to bombard all detectors (30 Sec). It was found the values of the diameter, number of tracks, removal layer thickness, track Diameter growth velocity VD by using the etching solution (NaOH +water) Solution greater than the values in (KOH + water) solution. the results showed excellent agreement with the outcomes of others who utilized different normalities.