Metro engineering vehicle is the key equipment to ensure the safe operation of metro system, and its overall dimension design is subject to strict restrictions imposed by metro gauge. This paper takes a specific metro engineering vehicle model as the object and 3 cross-sections susceptible to danger from the object for dynamic envelope calculations with two methods, the CJJ 96 standard-based method and the vehicle dynamic simulation-based method. The CJJ 96 standard method requires calculation of all possible offsets of the vehicle during operation and superimposition with vehicle contour, while the vehicle dynamic simulation method requires a multi-body dynamics model of the metro engineering vehicle and dynamics simulation thereof to obtain the vehicle's dynamic offset for dynamic envelope calculation. The dynamic envelope calculated with the CJJ 96 standard method exceeds the vehicle gauge and the metro engineering vehicle does interfere with the structures and equipment in actual operation, which means that the CJJ 96 standard method delivers results reflecting better engineering reality. However, the dynamic envelopes obtained by vehicle dynamics simulation method are all within the vehicle gauge, which is inconsistent with the actual situation. The metro engineering vehicle's overall dimensions are modified according to the results obtained with the CJJ 96 standard method. The modified envelope meets the requirements of vehicle gauge and no interference occurs in subsequent operation, which proves the effectiveness of the CJJ 96 standard method in dynamic envelope calculation.