Along with the increasing economic development and increasing and increasing needs, the costs needed will be even greater, both for life needs and for businesses where the costs needed are mostly obtained from lending and borrowing activities. In these lending and borrowing activities, there are legal products used by the community in the form of guaranteeing goods to obtain financing. This is where fiduciary security is present to meet legal needs in guaranteeing lending and borrowing activities.The purpose of this study is to find out the application of fiduciary guarantee law No. 42 of 1999, The main objective of this study is to design an ideal legal reconstruction of the Fiduciary Guarantee Law No. 42 of 1999 so that law enforcement and legal compliance are being the ideal of this Act can be realized ideally and optimally. This study uses normative legal research which includes legal principles, legal systematics, legal synchronization, comparative law and legal history.There are 2 important findings in this study, First, there is uncertainty in sanctions in the Fiduciary Guarantee Law, so this makes the Law not have the power in the application of the law. Secondly, there is inconsistency and disharmony in the Fiduciary Guarantee Law and the Minister of Finance Regulation which are the implementing regulations, so that law enforcement from this law is not optimal as Normative Law and Fiduciary Law does not have forced efforts in terms of law enforcement for necessity in conducting fiduciary registration. Due to the weaknesses of the Fiduciary Guarantee Law No. 42 of 1999, researchers see that it is very necessary for an ideal Reconstruction of the Fiduciary Guarantee Law so that law enforcement and Legal Compliance can be realized with an ideal, Optimal and fulfilling sense of Justice.