The diagnostic criteria for nephrotic syndrome include massive proteinuria, with urinary protein greater than 3.5 grams/day, hypoalbuminemia, with plasma albumin less than 30 grams/liter, severe edema, and hyperlipidemia, which includes significant increases in plasma cholesterol and triglycerides. The first two criteria are essential for the diagnosis of nephrotic syndrome, while the latter two are secondary. Clinically, if the two necessary criteria are met, the diagnosis of nephrotic syndrome is established. Patients with nephrotic syndrome should undergo a renal biopsy to determine the pathological type and guide clinical treatment.