The invention provides a method for saving water and protecting seedlings of cotton in a serious saline and alkaline land. According to the method, optimal irrigation time and an optimal water amount are selected, so that optimal water conservation and saline and alkaline suppression effects can be achieved; the key point is that due to measures such as plastic film mulching and liquid mulching film spraying to seedling holes, enrichment of salt and alkali to a ground surface along with moisture evaporation can be reduced, and the content of the salt and the alkali in the soil of the ground surface can be reduced to the maximum extent, so that the purposes of saving water and protecting the seedlings of cotton in the serious saline and alkaline land can be achieved.