Abstract: In order to study the shear lag effect on the cracking load of concrete sandwich panels (CSPs), a CSPs simplified calculation model is established. By introducing the maximum shear lag coefficient, derived is a theoretical formula for calculating the cracking load under different loading conditions. Then, the finite element models (FEM) under different loading conditions are established by those parameters such as panel length, top wythe thickness, insulation layer thickness, bottom wythe thickness, connectors spacing and, diameter, and analyzed are their effects on the CSPs maximum shear lag coefficient and on the cracking load. The theoretical formula is compared, and its reliability is verified according to the FEM results. Finally, the theoretical formula applicability is clarified through the example analysis. The results show that increasing the panel length, bottom wythe thickness or reducing the connectors spacing can weaken the shear lag effect in the CSPs; that different load conditions have a significant effect on the CSPs cracking load; that ignoring the shear lag effect will lead to a larger error in the cracking load when CSPs is under four-point bending; that increasing the panel length, wythe thickness, insulation layer thickness, connectors diameter and reducing connectors spacing can increase CSPs cracking load; and that the theoretical calculation error is large when the connectors stiffness is weak.