Purpose Lung cancer (LC) is the most commonly diagnosed cancer and the leading cause of cancer-related deaths. More and more long noncoding RNA (lncRNA) are associated with cancer. This study aimed to assess whether plasma lncRNA could be used to diagnose early-stage LC and identify subtypes of LC. Methods For bioinformatic analysis, we used genetic data from the Cancer Genome Atlas, lung adenocarcinoma (LUAD), and lung squamous cell carcinoma (LUSC) datasets and a small cell lung cancer (SCLC) dataset from the Gene Expression Omnibus. Real-time quantitative polymerase chain reaction (RT-qPCR) was used to examine the relative expression of lncRNA in LC tissues and plasma samples. The patients' clinical information was obtained at the time of sample collection. Results According to public datasets, the lncRNA forkhead box D3 antisense 1 (FOXD3-AS1) was significantly upregulated in LUAD, LUSC, and SCLC tissues over controls. RT-qPCR assays confirmed this finding in LUAD, LUSC, and SCLC tissues and plasma samples. Even early-stage receiver operating characteristic analysis showed that plasma FOXD3-AS1 could be used to discriminate LUAD, LUSC, and SCLC from normal controls and identify LC subtypes SCLC. Conclusion FOXD3-AS1 is significantly upregulated in LC tissues and plasma. FOXD3-AS1 could be a potential biomarker for LC subtype identification and early diagnosis.