The purpose of a multi-parameter observation system for pit-surface is to achieve high-accuracy observations via electromagnetic signals in tunnels and on surface. The existing ground electromagnetic observation systems have high background noise with low field applicability. The existing non-polarized electrode and inductive magnetic sensors are difficult to operate in tunnels. To solve the problems, an electromagnetic observation system with chopper amplifier circuits for pit-surface has been developed. According to the non-contact electrode principle in the medical field, a non-contact electrode was developed for electric field observation to solve the difficulty of connecting tunnels to ground surface. A 3-axis audio magnetic sensor was developed to solve the existing problem of poor adaptability of large inductive magnetic sensors in narrow tunnels. In the meantime, a number of good improvements for field applicability have been made for the observation system, which greatly enhanced the efficiency of field operation. A series of indoor and field tests were performed, and results confirmed the validity and advancement of the multi-parameter electromagnetic observation system for pit-surface.