Objective To explore the predictive value of the size of lung adenocarcinoma presenting as ground-glass nodules (GGN) for invasiveness of lung adenocarcinoma, which measured by thin-slice chest CT in different window width and window level, and to increase awareness of GGN. Methods Retrospective analysis was performed on 47 patients with lung adenocarcinoma from January 2015 to March 2018. There were preoperative thinslice chest CT images and postoperative pathology of 49 GGN. The average diameter of GGN in the lung window (window wide: 1500HU, window level: -400HU), mediastinal window (window wide: 350HU, window level: 50HU), adjust window (window wide: 1300HU, window level: 50HU) was measured, which were analyzed with postoperative pathology. Results There were 32 invasive adenocarcinoma (IAC) in 49 GGN and 17 non-invasive adenocarcinoma: 13 microinvasive adenocarcinomas (MIA), 2 carcinomas in situ (AIS) and 2 atypical adenomatous hyperplasia. The GGNs according to 5mm diameter measured on the lung window and 5mm on adjust window and mediastinal window were differentiated as the IAC and non-IAC. The proportion of IAC was significantly increased in group with GGN average diameter greater than or equal to the boundary value. The sensitivity of the boundary value to IAC diagnosis was 62.5% (lung widow), 75% (adjust window) and 31.25%(mediastinal window), and the specificity was 88.24%, 94.12% and 100% respectively. Conclusions The size of GGN measured in different window wide and window level is associated with invasiveness of lung adenocarcinoma presenting as GGN. Comprehensive consideration of GGN size of lung adenocarcinoma presenting as GGN measured by chest thin-slice CT in different window width and window level has predictive value, which can provide a reference for operation scheme.