Abstract: To illustrate the fatigue performance of high strength steel welding structures in construction machinery, tests on fatigue crack growth of weldments made of HQ70, 1E0170 and WH60 steels were conducted. An automatic compliance crack length measurement system for fatigue crack propagation test was used in the experiments. The 3PB (three points bending) specimens were used to study the fatigue fracture behavior of these weldments. The thresholds and fatigue crack growth (FCG) rates were given with Paris-formula and three-parameter-formula. It is observed that the fatigue performance of HQ70 is better than any other steels under investigation. The qualities of weldment have great effects on fatigue performance of steels. Enough care must be paid while measuring the thresholds of weldments due to the wavy character of FCG rates.