The present invention belongs to the field of pharmaceutical technology and relates to transdermal Ligustrazine plaster and its preparation. It has Ligustrazine phosphate or Ligustrazine as active medicinal component and consists of medicine storing back, adhering layer, release controlling film, back lining layer and protective layer. It is superior to available Ligustrazine preparation forms inmedicine releasing are, transdermal rate and lasting release time, and has the features of determined curative effect, stable quality, high safety, etc. Animal experiments show that the plaster can retard the effect of ischemic to cerebral damage, inhibit thrombosis caused by tissue damage, prevent and treat cerebral embolism and maintain balanced medicine density in blood for 24 hr; and has light irritation to skin, no irritability and no toxic reaction.