Abstract: AIM　To study the optimum tableting pressure of aspirin-ethylcellulose (EC) matrix tablets using percolation theory. METHODS　To prepare aspirin-EC tablets which contain 40% aspirin using different tableting pressures. The dissolution curves of tablets were determined, the dissolution data were model-fitted with Higuchi and Ritger-Peppas equations. Putting the values of slope b of model-fitted and total porosity of tablets ε to the formula derived from percolation theory, the apparent diffusivity D and tablet dissolution parameter β could be calculated. Regression with D versus ε, β versus ε and β versus ε₀ could be obtained. RESULTS　The release of drug prepared under 9～18 kN obeyed Higuchi model equation, the tablets released aspirin with matrix diffusion mechanism, the drug release was moderate. When the pressure was lower than 9 kN, the drug release was too fast; when the pressure was higher than 18 kN, the drug release was too slow. CONCLUSION　Percolation theory could elucidate drug release mechanism more clearly. The optimum tableting pressure range of aspirin could be calculated, then tablets prepared under the pressure in this range could have a suitable dissolution rate.