High-entropy alloys (HEAs) are solid solution alloys containing at least five principle elements in equimolar or nearly equimolar ratios. As one of the core effects of HEAs, the long-range and the local lattice distortion is crucial in understanding the strengthening mechanisms. A HEA family CoCrMoxNiTiWy has been synthesized by adding Mo and/or W into the CoCrNiTi base alloy with emphasis on high-temperature applications. As the concentration of Mo and/or W element increases, the major phase changes from FCC to BCC. Minor intermetallic phases are also observed. The hardness values increase with the increasing Mo concentration, but decrease as W concentration increases. By performing neutron diffraction measurements, we aim to determine precisely the average crystal structure and study the relation between local lattice distortions and hardness by means of pair distribution function method.