This paper has developed a principle and method of the 3D damage environment spectrum of metallic calendar life, which is made through the operating temperature, humidity and time. It contains: actual mea-surement and statistics of the original parameter of the operating temperature; the formation principle of equal corrosion damage spectrum; 3D spectrum formation method made of the random combination of 3 parameters (temperature, humidity and time) of operating environment; then cases of various 3D spectrum of two regions, namely, Hai Nan and Chong Qing are provided. This 3D spectrum can form a multi-layer humidity and multi-layer temperature spectrum on the basis of calendar life calculation and test demand. Meanwhile, 3D spectrums of one-layer humidity with multi-layer temperature spectrum or 3D spectrums of any other random combination can be formed. Theoretically speaking, since these different spectrums are under equal damage, therefore the calendar lives of final calculation and test are the same. In this way, the inaccurate “ equivalent conversion” phase in the field of corrosion can be eradicated, making the determination of calendar life more reliable.