Abstract: The knowledge of differences between weed species in their relative capacity to capture growth-limiting resources provides information which can be used to predict competitive ability of weed. A field study was conducted to compare weeds growth indices to evaluate weeds competitive ability. The experimental design was a Randomized Complete Block (RCBD) with 3 replications. Treatments were consisted of increasing durations of weed which were established by delaying weed Removal Time (RT) to different corn growth stages. Growth analysis was performed by determining weeds growth indices. In this trial different weed species exhibited marked differences in growth indices during growing season. Compare to other weeds, Barnyard grass had the greatest leaf area index and weed growth rate from the beginning to the middle of growing season. However, redroot pigweed achieved its maximum growth later from the middle of growing season to the end of season and became the dominant weed for that time. Redroot pigweed had by far the greatest relative growth rate compare with other weeds. It reveals that barnyard grass was the dominant weed for the beginning of growing season. However, from the middle of growing season till the end redroot pigweed became the dominant weed.