The network structure of natural rubber (NR) achieved during vulcanization was analyzed using the model of rubber elasticity based on the tube concept, applied to the treatment of the stress-strain measurements. This theory allows the separation of constraint and crosslink contributions. Also, network parameters can be calculated. The crosslink level of the material was changed using different times and temperatures of cure. The change in the molecular parameters of the model with the degree of cure was estimated. The present research is useful for the precise determination of the chemical crosslink density of the NR network. The values were compared with those obtained by means of equilibrium volume swelling measurement.