A series of up-conversion luminescence materials of Y1.98-2xYb2xEr0.02SiO5(0.00≤x≤0.15) and Y1.736Yb0.24Er0.02Tm0.004SiO5 were synthesized by co-precipitation method.The absorption spectra from 400 to 1600 nm of Y1.98-2xYb2x Er0.02SiO5 (x=0.00,0.08) were compared, and the up-conversion emission spectra of all samples were investigated when excited by 976 nm opo laser. The decay curves of Er3+4S3/2(4F9/2)→ 4I15/2,Tm3+1G4→3H6,as well as the relationship between the blue up-conversion emission intensity and pumping power were measured,consequently, the possible up-conversion luminescence mechanisms of Er3+,Tm3+ in Y2SiO5 were discussed. The results show that X2-type monoclinic Ln3+(Ln3+=Er3+,Yb3+,Tm3+) co-doped Y2SiO5 phosphors have been synthesised under relatively low temperature of 1250 ℃, and the absorption intensity and bandwidth are remarkably increased by Yb3+ sensitizing around 976 nm. Up-conversion emission spectra has been analyzed and the results suggest that both the green and red lights increase first and then decrease with the increase of the Yb3+ doping concentration. However,the concentration quenching of the red light emission is higher, due to the forward (ETU3) and back (ETU4) energy transfer between Yb3+ and Er3+ ions; the blue emission occurs mainly through phonon-assisted energy transfer between Yb3+ and Tm3+ ions, which is a three photon absorption process.