This research project is mainly to discuss other category of secured obligation which is different from the statutory accessory ones, for example, sale by installments with the clause of retained title, where title to the thing is retained until the buyer fully pays the purchase price. Besides, in order to expand the amount of consumption via credit card, the issuing bank encourages primary card holders to apply for additional cards for their family members or the third parties. Additional card holders are not parties to this given credit card contract, however, clauses of standard contract formulated by the issuing bank always stipulate that additional card holders should be jointly obliged to pay for the debt of the primary card holders. Nevertheless, this kind of clauses deprives the secondary debtor, merely responsible for the provision of security, of the protection of his/her supplementary duty, and makes the secondary debtor become the primary one. Whether the secured obligation, without distinguishing a secondary debtor from a real debtor, has overstepped the necessibility to attain to its goal? Whether we should acknowledge its legality without limitation? These issues are significant ones which should be dealt with in the development of contract law. Furthermore, in the work contract, the proprietor always ask the undertaker to provide performance bond, or ask the guarantee bank to provide a letter of guarantee as performance bond, and with a clause requiring instant payment. Performance bond is to secure the performance of obligation, which the undertaker shall provide to the proprietor prior to the failure of performance. After the obligation being fulfilled, the proprietor is liable for refunding the performance bond. Moreover, whether the proprietor’s claim to invoke instant payment clause toward the guarantee bank is distinguished from that for indemnification toward the undertaker? After the guarantee bank pays the proprietor, with the view that it is an independent claim, the proprietor can still keep the performance bond provided by the undertaker. In this circumstance, whether such performance bond acquired by the proprietor has transgressed the reasonability and necessibility of the purpose and object of secured obligation? This opinion is reflected in many decisions made by the Supreme Court, and it deserves further discussion to explore the future development of contract law regarding secured obligations.