Fe25Co25Ni25Cr25-XMoX High Entropy Alloys were fabricated in mini arc-melter and then cast into 4mm diameter cylinders by injection casting technique and 1cm diameter cylinders by water quenching technique. Heat transfer modeling during solidification of FeCoNiCr HEA was simulated. Combining X-Ray Diffraction, Optical Microscopy, Scanning Electron Microscope, Energy Dispersive X-ray analysis, microhardness tests and compression tests, the influences of replacing Cr with Mo in Fe25Co25Ni25Cr25-XMoX HEA series on the microstructure and mechanical properties were investigated. Fe25Co25Ni25Cr25-XMoX HEAs with produce σ phase after annealed at 800℃ for 2h. HEAs with remain single FCC solid solution phase after annealing at 800℃ for up to 24h. Fe25Co25Ni25Cr16Mo9 HEA shows a compression strength of ~1.4GPa and fracture strain >0.8. Fe25Co25Ni25Mo25 has an ultimate compressive strength of ~1.7GPa and fracture strain of 0.24.