The teaching efficiency of college physics experiment is affected due to the large systematic errors in the manually measuring system of water vaporization heat，since the steam condensed severely，the condensate water mixed into the calorimeter and the steam temperature is difficult to be measured accurately.In this paper，the structure of the experimental device is improved.A steam filter with four orifices bulb is selected instead of the traditional steam filter，and the actual steam temperature is measured in it.An electric heating sleeve with adjustable temperature is installed on steam pipe which can prevent vapor condensation.The systematic errors are reduced.The experimental results have shown that the improved device is stable and reliable with low cost and high measurement accuracy.The relative deviation between the measured results and the accepted value can become less than 3% instead of 10.4% before the improvement.