Semiconductor polymers poly( 3-dodecylthiophene-2,5-diyl), regioregular ( PDDT) and poly[ 2,5-bis( octyloxy)-1,4-phenylenevinylene] ( BO-PPV) are prepared by thin films by a spray method under vacuum. The formation process and properties of these polymer thin films are described. The dilute solution was used to prepare thin film by this method; annealing the semiconductor polymer thin film under vacuum would highly increase their surface smoothness.