Abstract. Studies show that the green open space (GOS) is beneficial to visitors' mental and physical health and has positive social values. This study took four global cities as examples, namely Shanghai, Tokyo, New York and London. The per capita area, the coverage rate and the availability of GOS were calculated in this study. Then the GOS was classified according to the scales and morphological features. And the author analyzed the relations between availability and spatial patterns. The results showed that the four cities could be classified into two classes. Shanghai and Tokyo are high-population-density cities with medium GOS coverage and availability, and New York and London are medium-population-density cities with high GOS coverage and availability. It was found that the high GOS coverage rate did not necessarily lead to a higher availability. Shanghai and London could increase the amount of small GOS to ease the shortage of availability. And London and Tokyo could consider adding linear GOS to improve the connectivity of GOS.