According to the difference of guarantee types, buyandsell guarantee can be divided into real right guarantee and obligatory right guarantee. Real right guarantee is alienation guarantee and has no security interest position.The buyandsell contract represented by the debt guarantee is invalidated due to the hypothetical representation of both parties, and the substitution repayment agreement is invalid because it violates the prohibit mortgage, hence having no guarantee effect.The creditor has no right to require the debtor to deliver the subject matter of the transaction, but after the delivery of the subject matter, he or she can exercise the liquidation right to protect his or her own rights. The liquidation right has no priority for repayment.