OBJECTIVE： To optimize the formulation of Cilnidipine sustained-release tablet， and study its drug-release mechanism. METHODS： Solvent method was adopted to prepare the cilnidipine solid dispersion， then Cilnidipine sustained-release tablet was prepared by using hypromellose K4M （HPMC K4M） as release material. Using comprehensive scores of cumulative release degree in 2， 6， 12 h as indexes， single factor method and Box-Behnken response surface method were used to screen the amounts of HPMC K4M and ethyl cellulose （EC）， lactose-microcrystalline cellulose （MCC） ratio in formulation of Cilnidipine sustained-release tablet， and verification test was conducted. The drug-release mechanism of Cilnidipine sustained-release tablet was investigated by model fitting way. RESULTS： The optimal formulation was as follow as 25％ of cilnidipine solid dispersion， 30％ of HPMC K4M， 10％ of EC， lactose-MCC ratio of 1 ∶ 1 （m/m）. The adhesive was 5％ PVPP ethanol solution and the lubricant was 0.5％ magnesium stearate. The cumulative release degrees of prepared sustained-release tablet in 2， 6， 12 h were （21.4±3.3）％， （62.9±2.8）％， （85.4±0.5）％ （n＝3）， relative error of which to predicted value 25％，60％，90％ were 14.4％，4.8％ and 5.1％. Release curve showed the highest fitting degree with the first-order release model， conforming to non-Fick diffusion. CONCLUSIONS： Cilnidipine sustained-release tablet with sustained-release effect is successfully prepared by optimized formulation.