The injection, mixing and atomization characteristics of transverse liquid jet in liquid-fueled scramjet are the determining factors for the efficiency of the combustion chamber. An origin image analysis method, without any threshold choosing section, was developed in house to get the unique unstable boundary of the transverse jet without any manual effects. The lateral extension boundary capturing method, which is based on PIV technique and the corresponding image analysis method, was developed to illustrate the lateral outer boundary of the jets. Results from targeted and comparative experiments indicate that, compared with the single jet case, the penetration heights and lateral extension become larger in the assemble jets cases. A larger distance between the streamwise assembled double injectors contributes to a higher penetration height of the jet.