The general corrosion behavior of zircaloy-4 alloy in simulated pressurized water reactor(PWR) primary loop was studied using still autoclave, the corrosion test lasted for 8 000 hours. The thickness of oxide film was measured and calculated, the mass gain and general corrosion rate were quantitatively evaluated. The results show that the corrosion curves of inside and outside pipes of zircaloy-4 alloy are cubic law at the initial stage，and they are linear after 2 500 h.As for inside pipe, the fitting curve is y=2.473 47x1/3 from 0 h to 2 500 h; when the time is over 2 500 h, the fitting curve is y=9.033 43+0.013 22x.As for outside pipe， the fitting curve is y=2.473 47x1/3 from 0 h to 2 500 h; when the time is over 2 500 h， the fitting curve is y=9.498 49+0.013 11x. The thickness of inside pipe oxide film is 32.4 μm after 4.5 years, equivalent to 20.8 μm of metal substrate, which is much less than ten percent of inside pipe wall thickness. The thickness of outside pipe oxide film is 31.5 μm after 4.5 years, equivalent to 20.2 μm, which is much less than ten percent outside pipe wall thickness. After 4.5 years corrosion test simulated pressurized water reactor primary loop considering the influence of flow velocity and irradiation， the corrosion depth of inside and outside pipe is much less than ten percent of the wall thickness of zircaloy-4 alloy cladding.