The invention relates to the technical field of laundry detergent, in particular to herbaceous alkalescent laundry detergent and a preparation method. The herbaceous alkalescent laundry detergent is prepared from the following raw materials in parts by weight,: 19-21 parts of soapwort extracting solution, 6-8 parts of metasequoia glyptostroboides essence, 2-4 parts of coconut oil diethanolamide and 67-73 parts of water. No other chemical agents are added except the coconut oil diethanolamide which is known as a non-toxic harmless additive, so that the herbaceous alkalescent laundry detergent has natural and healthy effects; the soapwort extracting solution subjected to extraction has a good washing action, and the soapwort extracting solution is in combination with volatile essential oil and anti-bacterial components extracted from metasequoia glyptostroboides so that fresh smell, a sterilization effect and an anti-bacterial effect can be provided.