IntheSino-Americantradeofgoods，themechanicalandelectricalproductsarethebulk commoditybetweenChina andtheUS. Therefore，theresearchonin-industrytradeof dynamicmachines and equipments is helpful to improve the trade competitiveness of China's mechanical and electrical products. Through G-L index，in-industry absoluteness，margin in-industry trade index，Greenaway and Milner，the in-industry trade level and internal structure are analysed and given relevant suggestion.