Abstract: As the fiber-reinforced engineering cementitious composite (ECC) has good multi-crack cracking characteristics and tensile ductility, utilizing ECC as the initial support in large deformation potential tunnels can effectively avoid the problem of cracking and cracked block falling of the shotcrete layer. For the tunnel project near the desert, in order to solve the problem of lack of river sand resources, the desert sand is used to completely replace the ordinary river sand. The mix ratio of jettable PVA/PE hybrid fibre desert sand ECC which can be used as tunnel initial support was determined by experiments. The influence of the relative volume content of PVA/PE fibre and the ratio of fly ash in cementation materials on the mechanical and working properties of desert sand ECC was studied, and a three-fold tensile model of desert sand ECC was proposed by considering the fibre impact factor λ. The research results show that: when the proportion of fly ash in cementitious material is 0.55, the slurry of desert sand ECC has good fluidity, and the compressive strength, tensile strength and ultimate tensile strain at 28 d reach 64.90 MPa, 6.18 MPa and 5.96%, respectively, and has the multi-cracking and strain-hardening characteristics, which can meet the requirements of the strength indexes of C40 jettable desert sand ECC; when the proportion of fly ash in the cementitious material is 0.60, the compressive strength, tensile strength and ultimate tensile strain at 28 d reach 53.57 MPa, 4.50 MPa and 3.84%, respectively, which can satisfy the strength index of C30 jettable desert sand ECC. The comparison between model calculation results and test ones shows that the proposed tensile constitutive model of desert sand ECC taking the fibre impact factor λ into consideration can describe its tensile stress-strain relationship very well.