In the paper，the SWY-Ⅱ and the LN-3A instruments are contrasted from the seven aspects of stability，data consistency，internal quality，systematic drift，water-seismic waves，barometric effect and natural environment interference at the Jingle well. The main conclusions are as follows: ①The two digital instruments are stable. ②The observation data of the SWY-II instrument coincided with the LN-3A instrument. ③The measurement accuracy of two instruments is basically the same. There is a good identity in the mean consistency of the two instruments. ④There is little difference in the tidal factor of M2 wave and the observation precision between the two instruments. ⑤The two instruments have systematic drift in varying degrees. ⑥There is a big difference in the vibration time and the ranges of the water-seismic waves between the two instruments. ⑦There is little difference in the barometric effect and the natural environment interference between the two instruments.