AIM: To compare the efficacy of 3% diquafosol sodium (DQS) eye drops at different frequencies in dry eye (DE) after femtosecond laser-assisted in situ keratomileusis (FS-LASIK). METHODS: In this prospective study, DE patients after FS-LASIK were randomly divided into two groups. All patients were administered routine anti-inflammatory and anti-infective drugs after FS-LASIK. Additionally, both groups were treated with DQS, at frequencies of 4 (DQS4 group) and 6 (DQS6 group) times daily. Corneal fluorescein staining (CFS) score, non-invasive tear breakup time (NIBUT), tear meniscus height (TMH), lipid layer thickness (LLT), and incomplete blink rate (IBR) were assessed in patients preoperatively and at 1wk, 1, and 3mo postoperatively. The Ocular Surface Disease Index (OSDI) questionnaire was also administered. RESULTS: Totally 119 patients (238 eyes) were randomly divided into the DQS4 group (60 individuals with 120 eyes) and DQS6 group (59 individuals with 118 eyes). From 1wk to 1mo after FS-LASIK, the CFS score in the DQS6 group decreased with statistical significance (P=0.014), while the DQS4 group showed an upward trend. Comparing with preoperative values, the NIBUT of both groups was significantly prolonged at various time points after FS-LASIK (P0.05), while the DQS6 group remained a little higher than preoperative values (P>0.05). The TMH levels in the DQS4 group increased significantly at 1wk postoperatively (P0.05). There was no significant difference in IBR and LLT between the two groups within 1mo postoperatively. At postoperative 3mo, the LLT in the DQS4 group was significantly higher than that in the DQS6 group (P