The invention relates to a device in an electromagnetic measurement while drilling system for receiving an electromagnetic signal with measurement data information sent underground on the ground and transmitting the signal to a data processing computer, and a method thereof. The device uses two antennas in a well field to receive an electromagnetic signal sent underground and a well field noise signal respectively; and the two signals enter a program controlled low noise preamplifier to be amplified through the coupling of an impedance converter, then enter a signal conditioning module for processing, and then enter a digital signal processing module through analog-to-digital conversion, and finally data is transmitted to a computer terminal through an interface module. The device is matched with a downhole electromagnetic signal transmitter to form the electromagnetic measurement while drilling system to form the information communication between underground and ground. The electromagnetic measurement while drilling system is not affected by drilling fluid medium, can perform data transmission without circulating a drilling fluid under any working condition, and can solve the measurement while drilling problem in gas drilling and aerated drilling.