Abstract: Bill theory is the theory of law constitution of the cause of bill debt.The doctrine mainly covers:contract theory,commen release theory,amended release theory,creation theory and the theory of two phases.Each of these theories of bill has advantages and weaknesses.The theory of two phases of negotiable instrument behavior however is more reasonable to the interpretation of the correlative problem of bill.In our law of bill,the three clauses about the theory of negotiable instrument behavior adopt three different bill theories.This leads to the conflict and chaos of the theory of negotiable instrument behavior.Therefore,to achieve the same applicable bill behavior theory,bill theory in our law of bill should be built on the basis of the theory of two phases,and the terms above should be amended.