Aims: The serratus anterior plane block (SAPB) has commonly been utilized as a regional anesthesia technique for pain management in various upper chest surgical procedures. The purpose of this study was to investigate the analgesic effect and pharmacokinetics of ropivacaine in continuous SAPB undergoing VATS. Methods: This prospective randomized study included patients scheduled for elective VATS. Patients first received a bolus of 20 ml of 0.2% (Group L) or 0.375% (Group H) ropivacaine that was administered beneath the serratus anterior muscle. The pump was connected to the catheter for continuous administration within 48 hours postoperatively, in which a background infusion at a rate of 7 ml·h−1 of low-dose at 0.2% (Group L) or high-dose at 0.375% (Group H) of ropivacaine was administered. The main results were to compare the analgesic effects and analyze the pharmacokinetics of different concentrations of ropivacaine. Results: Eighty-eight patients agreed to participate in the trial and were recruited. The VAS scores in Group H at 12, 24, and 48 hours postoperatively at rest and on coughing were significantly lower than those in Group L. The peak values of total ropivacaine plasma concentrations were observed at 48 hours (2.01 μg·mL−1 for Group L and 2.93 μg·mL−1 for Group H), which were far below the theoretical toxicity threshold. Postoperative rescue analgesia, complications, and other outcomes did not differ significantly. Conclusions: In VATS patients, the analgesic effect of 0.2% ropivacaine for continuous SAPB was not inferior to that of 0.375% ropivacaine, and the blood concentration of 0.2% ropivacaine was