As the core component of underground internal combustion scraper, whether the engine is selected appropriately or not directly affects the power, economy, noise, reliability, life and environmental protection of the whole underground scraper. This paper takes the existing WJ-1 underground internal combustion scraper of a company as an example, through the market positioning, power demand analysis, legal and regulatory requirements analysis and space arrangement analysis, combined with the characteristic parameters of three kinds of engines, establishes three-dimensional model through UG, and carries out the comparative analysis of different schemes, and finally selects the optimal scheme.