"Global Engineering Education Accreditation" (GEEA) is an internationally accepted quality assurance system for engineering education in universities, and technology competitions for college students are also considered important approaches to achieve the educational objectives and meet graduation requirements of GEEA in practice aspects. In this paper, the competency of guiding teachers of technology competitions for Chinese college students is evaluated through a case of "National Competition of Transportation Science and Technology for Students" (NACTranS). Firstly, 7 theoretical hypotheses of the modified "structural equation modeling" (SEM) for competency were developed by concentrating on some principles pertaining to the key concepts of GEEA. Secondly, competition results were set as the dependent variable and 3 dimensions of competition (topic selecting, works producing and team managing) were set as the independent variables under the modified SEM. Meanwhile, both administrative ranks and regional locations of universities where guiding teachers work were set as intervening vectors so as to explain the formation mechanisms of competency. Thirdly, a case study of NACTranS data from 68 universities in China's mainland was done through modified SEM calculating. The conclusions indicate that competency of guiding teachers is not only represented by 3 dimensions but also indirectly manipulated by 2 intervening vectors. According to the case calculating by modified SEM, the determinant of guiding teachers' performance in topic selecting is the administrative ranks of universities, whereas their performance in works producing is dictated by the regional locations of universities. Various improvements on the competency of guiding teachers can be carried out in schools of engineering in Chinese universities, such as sufficient academic communications, efficient industry-university-research cooperation and so on.