The influence of temprature T on the critical in-plane magnetic field range for the break-down of vertical Bloch line (VBL) chains within the stripe Bloch domain walls with ordinary hardness in magnetic bubble films of LPE garnet is studied experimentally, We find that there exist two characteristic tempratures, T(1)0 and T(2)0, with the former slightly lower than the latter and both higher than room temprature Tr, such that at any T∈[Tr,T(2)0] there is a T-dependent critical range, [Hip(1)(T), Hip(2)(T)]，of in-plane magnetic field Hip: all VSLs keep stable when Hipip(1)(T)，V BLs disappear gradnally as Hip increases when Hip(1)(T)ip ip(2)(T), no VBL remains when Hip > Hip(2)(T), The lower and upper limits as well as the width of the critical in-plane field range all decrease as T increases, and the former two reach zero at T(1)0 and T(2)0，respectively. The ratio Hip(2)(T)/Hip(1)(T) tncr-eases with temperature elevating, slowly at lower T including Tr where this ratio is about 21/2 and rapidly near T(1)0. Some theoretical arguements are presented.