The performance of heterojunction polymer solar cells (PSCs) based on poly(3-hexylthiophene) (P3HT) and ［6, 6］-phenyl C61-butyric acid methyl ester (PCBM) blends was investigated by changing P3HT∶PCBM film fabrication procedures with fast growth and slow growth methods, respectively. The optimal time of slow growth of P3HT∶PCBM films was gotten after we systematically changed spin-coating time and preset time before annealing blended films. When P3HT∶PCBM film was spin coated at the speed of 800RPM and spin time ranged from 50 to 80 sec, and then put in petri dish for 30 min before annealing blended films, the power conversion efficiency (PCE) of PSCs reached 3%. Yet PCE of PSCs based on P3HT∶PCBM with fast-growth was only 1.8%. The improved PCE is attributable to the reasonable phase-separation between P3HT and PCBM blended film, which boosted carriers transport and hop. The result indicates that half an hour of preset time for P3HT∶PCBM films before annealing can efficiently finish the slow-growth of blended films, which can save time and decrease cost to fabricate efficient PSCs.