A field experiment was conducted to investigate the effects of intercropping time and planting density on land and energy utilization of melon/sunflower intercropping system. The results showed that the land equivalent ratios (LER) of the intercropping treatments were greater than one, indicating significantly increased land utilization rate of melon/sunflower intercropping system. The solar energy utilization efficiencies of other intercropping treatment were significantly higher than that of the monocultured melon except in the fruit expanding period, but were significantly less than that of the monocultured sunflower except for the 45cm spaced intercropping treatment which showed similar solar energy utilization efficiency with monocultured sunflower. Melon/sunflower intercropping significantly increased the leaf area index which was also affected by planting density. The adjustment of intercropping time could prolong the photosynthetic period resulting in an increased dry matter accumulation and solar energy utilization efficiency. A quadratic parabolic relationship was found between leaf area day (LAD) and solar energy utilization efficiency. As the crop population density increased, LAD and assimilates accumulation also increased until it reached a peak, afterward the increased LAD could not result in further accumulation of assimilates.