Poly(amic acid)(PAA) was prepared by reaction of bicyclo(2,2,2)oct-7-ene-2,3,5,6-tetracarboxylicdianhydride(BTDA) containing double bond for crosslinking and bis[4-(3-aminophenoxy) phenyl] sulfone(BAPS) in N,N-dimethylacetamide(DMAc). The cast film of PAA was heat-treated at different temperatures to create polyimide(PI) films. With increasing thermal crosslinking temperatures from 250 to $350^{circ}C$, the thermo-mechanical properties, degree of crosslinking, and optical transparency of the cross-linked PI were investigated. The maximum enhancement in the thermo-mechanical properties was observed at a heat treatment condition of $350^{circ}C$. However, the optical transparency was found to be optimal for $250^{circ}C$ heat treatment. The degree of crosslinking in NMR was determined to be 85% to 93% with increasing annealing temperature conditions from 250 to $350^{circ}C$.