Objective To investigate the nature of the suprachoroidal fluid by detecting the concentration of total protein (TP), lactate dehydrogenase (LDH), albumin (ALB), total cholesterol (CHOL), total bilirubin (TBIL) in suprachoroidal liquid of patients who have rhegmatogenous retinal detachment with choroid detachment (RRDCD). Methods Eighteen RRDCD patients (18 eyes) who underwent vitrectomy were enrolled in this study. There were 10 males (10 eyes) and 8 females (8 eyes), 8 right eyes and 10 left eyes. There were 8 patients with age of ≤55 years, 10 patients with age of ＞55 years. There were 7 patients with duration of ≤30 days, 11 patients with duration of ＞30 days. There were 7 eyes with diopters of ≥−6.0 D, 11 eyes with diopters of ＜−6.0 D. There were 11 eyes with class C proliferative vitreoretinopathy (PVR), 7 eyes with class D PVR. Suprachoroidal fluid samples were collected from all the patients, and took preoperative serum samples as RRDCD group. Ten serum samples of normal people were set as control group. The concentration of TP, LDH, ALB, CHOL, TBIL in all the subjects were measured. The properties of the suprachoroidal fluid were identified by Light standard and concentration standard of ALB, CHOL, TBIL. Results There was no difference on the concentration of TP, LDH, ALB, CHOL, TBIL from suprachoroidal fluid samples in the patients with different age, sex, eyes, diopter, PVR grade (P＞0.05). There was no difference on the concentration of TP, LDH, ALB, CHOL, TBIL from preoperative serum samples in the patients between RRDCD group and control group (P＞0.05). There was no difference on the concentration of ALB and CHOL from suprachoroidal fluid samples and preoperative serum samples in the RRDCD patients (P＞0.05), but there were significant differences on the concentration of TP, LDH, TBIL (P＜0.05). According to the Light standard, there were 17 cases of exudates and 1 case of transudate. According to the concentration standard of ALB, CHOL and TBIL, there were 14, 18, and 16 cases of exudates, and 4, 0, and 2 cases of transudate, respectively. There was no difference on the identification result of Light standard and concentration standard of ALB, CHOL, TBIL (χ2=2.090, 1.029, 0.364; P＞0.05). Conclusion The suprachoroidal fluid of RRDCD patients composed of TP, LDH, CHOL and TBIL. The suprachoroidal fluid is more likely to be exudate.