1. A method for constructing component fault tree based on physics of failure, comprising: establishing, based on common characteristics of component physics of failure and according to six layers based on physics of failure and category of the component, a fault information database containing information of the six layers based on physics of failure; constructing, based on the fault information database and according to the six layers based on physics of failure and logical relationship of physics of failure, a component fault tree of n levels of events of six layers based on physics of failure, wherein n is greater than or equal to 6; and simplifying the fault tree by means of failure mechanism sub-tree transferring and fault module sub-tree importing, wherein the step of establishing a fault information database further comprises: determining, based on the common physical characteristics of component physics of failure, six information layers based on physics of failure, namely: information layer of fault mode, information layer of failure mode, information layer of failure site, information layer of failure mechanism, information layer of mechanism factor, and information layer of influencing factor; and classifying and organizing failure cases and failure information, and establishing, according to the six layers based on physics of failure, fault information database of the six layers based on physics of failure.