Brownian dynamics simulations arc used to study the formation process of colloidal gels and the effect of particle concentration on their rheological properties. To model the interaction between particles, we adopted an R-shifted 12-6 Lennard-Jones (LJ) potential, which allows independent control of the particle size and attractive range. For a short-ranged potential, the percolated network characteristic of a gel exhibited a viscoelastic behavior of weak gels. The storage modulus (G') increased with the particle concentration increase. Moreover, the dependency of storage modulus (G') on the particle concentration followed a power law function, which is commonly reported in the literature for experimental data. Simulating frequency sweep tests showed that the system behaved as a liquid-like or solid-like Material, depending on the frequency applied. The crossover frequency, i.e., the frequency at which G' and G '' are equal, appears to shift slightly to lower values when the particle concentration increases, suggesting a more solid-like behavior for systems with higher particle concentration. During gelation, the storage modulus increases is a stretched exponential and reaches a constant value at long times.