The invention discloses a bar water tank reverse self-decision temperature-control intelligent calculation method based on a cut-and-try method. The method comprises the steps as follows: 1) calculating temperature distribution of a rolled piece; 2) calculating internal and external temperature distribution and the load of a water supply system when loading the rolled piece on a cold bed under combination of different water tanks; 3) searching water tank switching combination which does not cross the border with a surface layer temperature value and difference between internal and external temperatures as objective functions; 4) trying to regulate the size of a water flow valve of each water tank one by one according to a preset scale value with the minimum load of the water supply systemas an objective function; and 5) calculating an overall time-temperature evolution curve of the rolled piece after scales of water flow valves are lowered, comparing the time-temperature evolution curve with an expected cct cooling path, and ending and exiting the procedure after meeting the requirement. The method realizes control parameters of each water tank by rapid self-decision large-water-flow quick cooling, and ensures that the rolled piece obtains ferrite and pearlite to realize mechanical properties at martensite formation temperature or above at the highest cooling speed according to refined water-cooling regulation structure property requirements.