We study a particular category ${cal{C}}$ of $gl_{infty}$-modules and a subcategory ${cal{C}}_{int}$ of integrable $gl_{infty}$-modules. As the main results, we classify the irreducible modules in these two categories and we show that every module in category ${cal{C}}_{int}$ is semi-simple. Furthermore, we determine the decomposition of the tensor products of irreducible modules in category ${cal{C}}_{int}$.