[en] ¹²⁵I-iothalamate or Glofil-125 has been widely applicated in the US more than half a century. It mainly applies to the evaluation of glomerular filtration rate(GFR), particularly a very important role in liver and kidney transplant patients on monitoring of renal function. This is a simple, accurate method. However, most of the current domestic use of endogenous creatinine clearance rate, ⁹⁹Tc^m-DTPA renal dynamic imaging or ⁹⁹Tc^m-DTPA double plasma method to determine the GFR. However, these methods had a limited value to assessment GFR. This article describes the system ¹²⁵I-iothalamate principles, methods, clinical applications, radiation safety, etc., in order to lay the foundation for domestic clinical application. (authors)