Research conclusions:From the research on 40. 5 m steel track girder forChongqing light rai,l it is concluded the vertical deflection is 0. 044 7 m under the static and active live load of train. Under the most unfavorable working condition, themax compressive stress in the top slab ofmid -span is145. 0MPa, themax tensile stress in the bottom slab is128 MPa and the max shearing stress in the web near the bearing is 47. 4 MPa. The lateral center distance between two box girders is3. 7m, andB /L>1 /20. The fatigue stressofactive load is from -70. 5MPa to 73. 7MPa. Through calculation of the real bridge, the natural vibration frequency of the lateral first step of the bridge body is 4. 201 2 Hz and satisfies the index requirement of "Code forDesign of Straddle Monorail Transit". Through precise control of the design and construction, the line shape of steel track girdercompletelymeets the requirements ofmonorail vehicle operation and comfort of passengers.