Abstract: The effect of filling factor of receiver coil and the construction parameters of reciever coil on sensitivity of NMRspectrometer and The relationship between the limitation of Signal-Noise ratio for NMR signal and the tested Signal noice ratio for double T-bridge circuit have been discussed, An improvement has been taken to normal receiver coil (it is wound outside a tube which has 7mm O.D. and 6mm I.D.), The reciever coil is put inside the tube against its wall. It has been proved by experiment that using the CH₂₀₃ NMR spectrometer (made by Beijing Analytical Instrument Factory) with 5mm O.D.tube and 1% ethyl benzene, The sensitivity is raised from 20:1 (by normal receiver coil) to 30:1 (by improved reveiver coil).