The aim of the study is to discuss the effect of postprandial insulin level on blood pressure in elderly patients by comparing the blood pressure, blood glucose, and insulin levels between patients with postprandial hypotension (PPH) and non-PPH over 80 years old during fasting and within 2 h after meal, and observing the changes of parameters in patients with PPH before and after treatment with acarbose. Twenty-five PPH patients and 27 non-PPH patients were selected. The blood pressure, blood glucose, and insulin levels during fasting and within 2 h after meal were monitored. Patients with PPH were treated with acarbose. All parameters were checked one week later. (1) Preprandial blood pressure in PPH group was significantly higher than that in non-PPH group (152.00 ± 15.62 mmHg vs. 136.40 ± 14.12 mmHg, P < 0.05). (2) The maximum decrease of postprandial systolic blood pressure (SBP) in PPH group was significantly increased compared with that of the control group (32.20 ± 13.19 mmHg vs. 9.67 ± 8.38 mmHg, P < 0.05). The maximum increases of postprandial blood glucose and insulin levels were significantly higher in PPH group than in the control group (P < 0.05). (3) After acarbose treatment, the decrease of postprandial SBP in PPH group was significantly reduced compared with that before treatment (22.67 ± 6.98 mmHg vs. 32.60 ± 9.55 mmHg, P < 0.05); the increase of postprandial blood glucose was also significantly reduced in PPH group (2.37 ± 1.63 mmol/L vs. 3.39 ± 1.62 mmol/L, P < 0.05); the increase of postprandial insulin level was reduced significantly in PPH group (12.09 ± 3.96 mU/L vs. 22.33 ± 1.78 mU/L, P < 0.05). (4) There was no correlation between the maximum decrease of postprandial SBP and the maximum increase of blood glucose (r = -0.008, P = 0.961), but the maximum decrease of postprandial SBP was positively correlated with the maximum increase of insulin (r = 0.381, P = 0.032). PPH tends to occur in elderly people with elevated basal blood pressure before meal. PPH is associated with an abnormal increase of postprandial insulin secretion. Reducing the increase of postprandial insulin is one of the mechanisms of acarbose in the treatment of PPH.