The upconversion luminescence phenomena induced by 966 nm diode laser in Er:ZBLAN and Yb、 Er:ZBLAN glasses are studied. A new kind of quasi-avalanche up-conversion luminescence phenomenon is found. The results calculated from state rate equations are coincident with the experiment. When cross-relaxation P between Er3+ ions is very small, up-conversion fluorescence intensity enhances gradually along with the increase of pumping laser power and tends gradually to saturation; when cross-relaxation P is large, duo to the large energy cross-transfer of Yb、 Er:ZBLAN glass between Yb3+ and Er3+ ions, the upconversion excitation velocity R of Er3+ ion is high enough to lead the up-conversion luminescence having a steep raise before it gets saturation. This is the phenomenon of “second uprising” observed in the experiment induced by quasi-avalanche effect.