Based on the investigation of crossover cooperation cases of reading promotion in the provincial and vise-provincial libraries, the paper analyzes the characteristics and deficiencies of crossover cooperation of public libraries’ reading promotion. The findings of this study include: the content of crossover cooperation mainly focuses on resource optimization, space construction, and activity development, while there is a gap between the supply and the actual demands of the public; the cooperation objects are mostly public welfare groups, and there is little cooperation with profitable institutions; crossover cooperation alliances mainly involve specific type and comprehensive type, and the management mechanism is relatively loose. Then, the paper further proposes the promotion strategy of crossover cooperation of public libraries’ reading promotion: demand-oriented deepening cooperation content; taking the initiative to expand cooperation objects; establishing a mechanism to ensure the high-quality development of the alliance.