保留最后2位为小数,然后逢3位打一个,号 double a = 232344234.98; string t = string.Format("{0}", a.ToString("F2")); string t1 = t.Substring(0, t.Length - 3); string result = ""; for (int i = t1.Length - 1; i >= 0; i--) { result = t[i] + result; if ((t1.Length - i) % 3 == 0) { result = "," + result; } } if (result[0] == ',') result = result.Substring(1); textBox1.Text = result + t.Substring(t.Length - 3);