Abstract: AIM　To study the drug release mechanism and dissolution kinetics of aspirin-ethylcellulose (EC) matrix tablets using percolation theory. METHODS　The dissolution curves of aspirin tablets with different quantities of aspirin were determined. The dissolution data were model-fitted. The percolation threshold of aspirin was obtained after a series of calculations using percolation theory. RESULTS　When the content of aspirin was between 30%～60%, the drug release obeyed Higuchi model equation, the tablets released aspirin with matrix diffusion mechanism; when the aspirin quantities were high, the dissolution kinetics were approximately of zero order kinetics. The calculated critical porosity was 0.313. CONCLUSION　Percolation theory could elucidate drug release mechanism more clearly. The percolation threshold of aspirin can be calculated, then the range of drug content of tablets which has a suitable dissolution rates can be dertermined.