Oriented polysilane LB films are cross-linked in order to increase their durability toward heat and deep UV lights. When oriented polysilane LB films without cross-linking are exposed to UV light polarized in the direction parallel to the silicon chains, the order parameter decreases because of scissions of the silicon chains. The order parameters also decrease when thin films are heated; this is a result of disorientation rather than thermal decomposition. The durability of the oriented polysilane LB films toward heat and UV irradiation increases considerably when they are cross-linked by exposure to HCl and HCHO vapor. The cross-linking of P2 (poly((3-hydroxyphenyl)hexylsilane)) is carried out without losing the polysilane orientation, however, in the case of P1 (poly(hydroxyhexyl)hexylsilane)), a decrease in the strength of the UV absorption was observed. Information on energy transfers within polysilane films is obtained by photolysis of oriented polysilane LB films.