A Titanium alloy composite reinforced with fiber-like TiB particles (TiB/Ti composite) has a good interface bond strength between the particle and matrix, as it is produced in-situ by a vacuum are remelting process. However, it is thought that damage, i.e. particle breakage, interface debond and so on, is more likely to occur under pre-working. In this paper, firstly an analytical model for the composite is developed to estimate effects of pre-working on elastic modulus by applying the Eshelbys equivalent inclusion method to two kinds of inhomogeneities, i.e. bonded and debonded fiber. Secondely type of damage due to a few kinds of pre-working is investigated experimentally. As a results, it is indicated that the particle breakage mainly occurs due to pre-straining in the particle orientation direction, while interface debond mainly occurs due to that in the perpendicular direction to the particle orientation. Finally good agreement between the analytical results base on the present model and the experimental ones is shown about reduction of elastic modulus with particle breakage.