Objective: To optimize formula of Hyperici Perforati Herba extract sustained-release tablets and evaluate its in vitro release mechanism. Method: With cumulative release rate of hypericin at different time points as comprehensive evaluation index

orthogonal test was adopted to optimize formula of Hyperici Perforati Herba extract sustained-release tablets by taking quality ratio of MCC to lactose

framework materials and the amount of HPMC as factors.Release mechanism of sustained-release tablets was investigated by in vitro release test. Result: Optimized prescription process was as follows:HPMC K15M 30%

MCC 6.4%

lactose 12.6%

magnesium stearate 1%.Drug release of Hyperici Perforati Herba extract sustained-release tablets in 2 h was 15%-30%

it was 40%-75% in 6 h and more than 85% in 12 h.In vitro release behavior was in line with Ritger-Peppas equation

release process was described by synergy of drug diffusion and skeleton corrosion. Conclusion: Optimized prescription process was reasonable and simple.In vitro release of these prepared sustained-release tablets was slow and stable

its release mechanism followed kinetic model of sustained-release tablets.