The invention discloses a degreased American cockroach and a preparing method and application thereof. The degreased American cockroach has the inosine content of 0.10 wt% or above and the grease content of 2.40 wt% or below. The degreased American cockroach has the low grease content and high inosine content, the side effects during pepticgastriculcer treatment can be remarkably reduced, and thenew option is provided for clinical medication. Meanwhile, the preparing method is high in degreasing rate, low in extraction pressure, low in extraction temperature, short in extraction time, free offunctional component damage, low in operation cost and suitable for industrial large-scale production.