Objective: To observe the effects of non-ionic hypoosmotic contrast agent, iopromide on ion channels in ventricular myocytes. Methods: The ventricular myocytes were isolated and whole cell patch-clamp technique was used to record the current density, steady-state activation curve and inactivation curve of sodium current (I _Na), L-type calcium current (I _Ca,L) and instantaneous outward potassium ion current (I _to) before and after iopromide administration. Results: Compared with that before iopromide administration, the current density of I _Na and I _Ca,L decreased obviously, the current density of I _to increased obviously after iopromide administration. While iopromide has no obviously effects on steady-state activation curve and inactivation curve. Conclusions: Iopromide may induce malignant ventricular arrhythmia by changing the duration of action potential of ventricular myocytes.