Our aim target was to find a suitable skin permeation enhancer for formulating a transdermal patch containing clonidine hydrochloride for treatment of hypertention diseases. Method: Using Franz diffusion cell to survey permeation capacity through rat skin of clonidine. Results: Among 13 studied chemicals belonging to 6 chemical groups, we found that alcohol group was a the most potential skin permeation enhancer group for clonidine hydrochloride and that 3-methyl-1-butanol could enhance the permeation of clonidine hydrochloride through rat skin in the highest ratio with permeation speed (Flux) was 41.0674 µg / cm2 / h and lag time (Tlag) was 1.9358 hour.