As is pointed out by Bartel et al. (AJ 112,1690, 1996), millisecond pulsars, by virtue of their stable rotations and sharp pulses of nearly point-source radio emission, can be used to tie Earth-orbit-oriented reference frames to Earth-spin-oriented reference frames with unprecedented accuracy through a combination of timing and VLBI measurements. CRL has been doing research on both timing and VLBI observations of Pulsars. As for the timing observation, we have developed the unique system using AOS and have been conducted the once a week regular observation of PSR1937+21 by using Kashima 34 m antenna since 1997. Recently we have been also observing some other pulsars by using Usuda 64 m antenna under the collaboration with ISAS. On Pulsar VLBI, under the collaboration with Levedev Institute, we have conducted the Japan-Russia 7000 km baseline pulsar VLBI observation by Kalyazin 64 m antenna and Kashima 34 m antenna, and have been developing the pulsar gating correlator. In this paper we will show the importance of the pulsar observation for tying the celestial reference frames and introduce the research activities of CRL on pulsar observations.