Mid-Field Calibration Technology (MFCT) has the advantages of low cost and easy implementation, while may not work correctly when modules are relatively large, due to its susceptibility to parallelism tolerance on phase calibration. This paper presents an improved method for MFCT which will effectively solve the problem without increasing the complexity of the system. Experimental results show that the improved MFCT is capable and accurate for linear array consisting of large subarrays as modules.