The energy performance of green roofs is influenced by many factors and the regulation differs significantly to each other in different climate zones. Previous research on green roofs confined to a single climate zone with a single set of properties, lacking comparative studies. In this study, a simulation was used for determination of the optimal parameter settings for green roofs in different climate zones. Firstly, a simulation model was established, and a field experiment examined the bias of the model. Leaf area index, plant height, and soil thickness were used as variables. Harbin, Beijing, Chongqing, and Guangzhou were selected as representative cities of four climate zones in China. For quantification of energy savings and indoor thermal comfort improvements, both cool and conventional roofs were simulated alongside green roofs for comparison. Optimal parameters of green roofs were found to be closely related to meteorological conditions in each city. In terms of energy savings, the recommended soil thickness and leaf area index in the four cities are 0.3 m and 0.5, respectively. The optimal plant height is 0.3 m, except in Beijing, where it is 0.1 m. Optimized green roofs are recommended for heating-dominated cities, while cool and green roofs perform similarly in cooling-dominated areas. (C) 2017 Elsevier B.V. All rights reserved.