A system for diagnosing a cooling water state applied to a cooling water pump control system is provided. The cooling water pump control system includes a speed controller that generates an output current instruction value of an inverter to provide power to a cooling water pump based on a difference between a speed instruction value of the cooling water pump and an actual speed measurement value of the cooling water pump. The system for diagnosing a cooling water state includes a pump speed prediction model unit that generates a speed estimation value to predict a speed of the cooling water pump based on the output current instruction value, and a pump state diagnosing unit that compares the speed estimation value and the actual speed measurement value to diagnose a circulation state of the cooling water.