Polyelectrolyte concentration dependence of gel point was experimentally investigated for alginate solution by addition of calcium ions. A power law relation was found between the gelation threshold fc and alginate concentration C with an exponent of -0.65±0.05. It was shown that the experimental results can be explained in terms of the scaling theories developed for vulcanization process and polyelectrolytes in semi-concentrated solutions. Based on the scaling analysis, a good agreement was obtained between the experimental and theoretical exponents.