The outcome of weight loss surgery is related to several factors, and for super-obese patients, the rate of weight loss failure and weight recovery after Roux-en-Y gastric bypass (RYGB) is high. Relevant studies have shown that the weight loss effect also correlates with total small bowel length (TSBL) and biliopancreatic (BP) and Roux limbs. However, there are few studies on the relationship between TSBL and anthropometric parameters, the BP limb, the Roux limb, and weight loss effect, and no relevant reports have been reported in China. The objective was to study the relationship between the total length of the small intestine and anthropometric parameters in the Chinese population. The effect of the Roux limb/biliopancreatic limb (RL/BPL) ratio on weight loss and diabetes remission in RYGB patients 1year after surgery was evaluated to find the appropriate ratio relationship. In this prospective study, 148 patients between the ages of 19 and 68years who underwent laparoscopic Roux-en-Y gastric bypass were enrolled. Height, weight, BMI, the BP limb, the Roux limb, fasting blood glucose (FBG), etc., were noted. To explore the correlation between the total length of the small intestine and these values. Subsequently, the 148 patients were followed up for 1year after surgery. The patients diagnosed with T2DM before surgery were screened out, and 56 patients were finally identified according to the postoperative follow-up, in which BPL = 50cm and RL = 150cm, 175cm, and 200cm, respectively. RL/BPL was divided into 3, 3.5, and 4 groups according to the proportional relationship to explore the relationship between RL/BPL and diabetes remission and weight loss. (1) The study included 148 patients (61 women and 87 men). The mean age was 35.68 ± 10.46years, weight = 127.46 ± 34.51kg, height = 167.83 ± 9.16cm, BMI = 44.94 ± 10.58kg/m2. The average TSBL value was 714.41 ± 101.08 cm. Linear regression analysis showed that TSBL was positively correlated with height, weight, neck circumference, chest circumference, waist circumference, and Roux limb. (2) Fifty-six patients with T2DM who were followed up 1year after surgery were divided into three groups. Group 1: BPL = 50cm, RL = 150cm (n = 20); group 2: BPL = 50cm, RL = 175cm (n = 26); group 3: BPL = 50cm, RL = 200cm (n = 10); RL/BPL = 3 was associated with higher weight loss than the other groups. The remission rate of diabetes did not differ between the three groups. TSBL was positively correlated with height, weight, neck circumference, chest circumference, waist circumference, and Roux limb. The TSBL of males was significantly higher than that of females. Among patients with T2DM who participated in the follow-up 1year after surgery, RL/BPL = 3 (n = 20) had greater weight loss than the other groups.