Objective : This experimental study was performed to investigate the effect of Coptidis rhizoma extract compared with quantity on Pseudomonas aeruginosa that induce keratitis. Methods : MIC was measured by dropping to 50 ${mu}l$ according to density Coptidis rhizoma extract(100%, 10%, 1%, 0.1%) compared with quantity(40g, 80g, 120g, 160g). Anti-bacterial potency was measured by the size of inhibition zone with change of volume. Results : MIC on Pseudomonas aeruginosa in Coptidis rhizoma extract compared with quantity(40g, 80g, 120g, 160g) was not showed all samples(100%, 10%, 1%, 0.1%). Conclusions : Coptidis rhizoma extract compared with quantity was not showed anti-bacterial potency on Pseudomonas aeruginosa. The results differ that Coptidis rhizoma extract was showed anti-bacterial potency in 1999 year. Anti-bacterial Potency of Coptidis rhizoma extract compared with quantity on Pseudomonas aeruginosa must be studied.