All publications of a country is a cultural heritage with the spirit of humanity, each National Library has to collect and preserve all publications produced in each country. Acquisition activity(Collection development) of each National Library is supported by a powerful legal deposit system. Therefore, this study has analyzed the legal deposit systems of the world countries, especially focussed whether or not the compensation for legal deposit, whether or not any sanction against not-depositing, Fine collection procedures against not-depositing, and the specific process for legal deposit. Based on these investigations, this study was to seek ways to contribute the legal deposit rates of National Library. It has proposed the following suggestions; Performing of legal deposit duty by itself, developing the system for supporting the legal deposit, establishing newly of legal deposit department, and improving the compensation for the legal depositor.