The average lifetime of cosmic rays in the Galaxy related with their confinement within the Galactic propagation halo, is a very important parameter to understand comic-ray propagation processes and the cosmic-ray origin. The measurement of the 10Be/9Be secondary isotopes ratio, as 10Be has half-life of 1.39 million years, can be used to constrain the propagation lifetime. The 6Li/7Li ratio, as both isotopes are secondary and stable, is expected to reflect the ratio between the production cross sections and therefore constitute a good check of the reconstruction method. Measurement of the lithium and beryllium isotopes ratio (6Li/7Li) and (10Be/9Be) as a function of the kinetic energy per nucleon from 0.5 GeV/nucl to 10 GeV/nucl based on data collected by AMS during the first 7 years of operation are presented. Prospects for measurement of the boron isotopic ratios with AMS-02 will be presented.