In order to meet the demand of new straddle monorail system,a kind of carbon fibre reinforced plastics(CFRP)-steel box concrete composite track beam is proposed.Through the numerical simulation experiment,the influence of the thickness of steel box upper chamber concrete on the maximum stress and vertical deflection of the top,bottom and upper chamber concrete in the middle span of steel box concrete track beam under load is investigated,and the appropriate thickness of steel box upper chamber concrete is obtained.On this basis,the flexural performance of rail beams in operation and maintenance stage is considered,and the flexural performance of rail beams is improved by pasting prestressed CFRP at the bottom of the beam.The variation trend of vertical deflection in the span of steel box con-crete variable section composite rail beams varies with the length of CFRP pasted at the bottom of the beam,and the design suggestions of CFRP-steel box concrete rail beams are given.The results show that the new type of CFRP-steel box concrete variable cross section strad-dle monorail rail beam has good flexural performance and can meet the needs of practical engineering.