The Pareto principle, also known as the 80/20 rule, describes this common pattern of sales concentration. But long tail principle, that expose the power of majority which had been put aside for a long time, rise as a new business strategy in web 2.0 era. In digital and online environment, as created the conditions that satisfy the need of diversity, long-tail effect has been relevant to all social cultures. This paper consider the long-tail effect from a library service point of view and develop library’s long-tail strategies. For the more, suggest practical plan about library long-tail based on library 2.0.