The fundamental motivation to study the non-mesonic weak decay (NMWD) of hypernuclei is that it provides the unique means for study of baryon-baryon weak interaction in SU3 (f) symmetry group. The new channel of NMWD, namely the recently confirmed three-body channel, seems to have a surprisingly big branching ratio so that it makes its accurate measurement prerequisite of the baryon-baryon weak interaction study. We report a new result of from E508 experiment of KEK-PS, though preliminary yet, which agrees with the previous result of C from the same experiment, those from FINUDA experiment and those of the recent theoretical predictions.