Abstract: Contradictions and dilemmas in study and application of contemporary engineering ethics is because that we only focus on seeking solutions to specific engineering ethics problems, but ignores analyzing the reasons of moral philosophy about "should be" in engineering ethics codes. At a metaphysical viewing, on one hand, through the discourse system of "engineers should…", the codes express people working in engineering activities should not only "do well" but also "live well" in the whole existence of human, nature, society and engineering, efforts to realize the "good life" as well. On the other hand, the codes provide many responsibilities to different actors in engineering activities. At the viewing of moral philosophy, through concluding and abstracting to reflect on engineering practice, "ought to be" incarnates a kind of ideal and positive manners of association and existence in engineering with people, nature and society in a long-term engineering practice. Meanwhile, it constitutes the normative view of engineering that formalizes the responsibility or obligation which "I" should undertake.