The research aims to know the effect of using a resistance vest in strengthening the arm propulsion force as a tool to increase water resistance against the body's forward movement and the extent of its effect on the length and frequency of the arm pull and consequently on the level of achievement in the 200m freestyle swimming event. In order to achieve the research objective, the researcher randomly selected (10) swimmers aged (13-14) years, and divided them into two groups, the first experimental (5) swimmers as an experimental group, and the second (5) swimmers as a control group. Both groups implemented the sections of the training curriculum prepared by their coach in all its details, except that the experimental group used the swimming vest as a resistance tool within the strength and overload training within the daily training unit components, and the control group used the traditional training method according to the method prepared by the coach. The researcher conducted the test before and after the research period, which lasted for 12 weeks, with three training units per week. The results achieved were statistically analyzed for both groups. The researcher found that the 200m swimming time had improved for both groups, but the group that used the swimming vest in arm strength development training was better, in addition to the noticeable increase in the length of the pull for the control group. Therefore, the researcher recommends using the swimming vest in arm strengthening training because of its impact on achieving the level of achievement in the 200m freestyle swimming