Abstract: Water-soluble amino acid fertilizers are a novel type of functional organic fertilizers for plants. To explore the influence of water-soluble amino acid fertilizers on plant growth, in this paper, fish product waste was utilized as the raw material, and water-soluble amino acid fertilizers were prepared by reasonably optimizing the ratio of feed to water, the types and amounts of proteases, and the hydrolysis conditions. Subsequently, through hydroponic experiments, fish protein water-soluble fertilizers with different dilution multiples were applied to wheat Bainong Aikang 58 to determine the optimal dilution multiple. Moreover, two fertilization methods, spraying and irrigation, were respectively adopted for tomato Xinzhongshu No. 4 to investigate the effects of different fertilization treatments of water-soluble amino acid fertilizers on the growth and development of crops. The results indicated that under the conditions of a 1∶3 liquid-solid ratio, with the addition of 0.1% alkaline protease and enzymatic hydrolysis at 50℃ for 4 hours, soluble amino acids with a total amount of 16.925 mg·g⁻¹ can be prepared using fish protein leftovers, and the proportion of amino acids that are easily utilized by plants is high（approximately 50%）. Hydroponic experiments indicated that the optimal application concentration of the fish protein amino acid water-soluble fertilizer was a 100-fold dilution（DB100）. DB100 significantly enhanced the germination rate and vitality index of wheat seeds and promoted the root length and root-shoot ratio of wheat seedlings（P ＜ 0.05）. With DB100 as the dilution standard, foliar spraying of amino acid fertilizer on potted tomato seedlings significantly increased the plant height（22.9%）, leaf area（38%）, and leaf chlorophyll content（33.3%）of tomato seedlings（P ＜ 0.05）, and decreased the malondialdehyde content in tomato leaves by 26.7%（P ＜ 0.05）. However, there was no significant difference between the application of water-soluble fertilizer through irrigation and the control CK（P ＞ 0.05）. The pot experiment demonstrated that foliar spraying of water-soluble fertilizer could directly provide nutrients to plants, which were readily absorbed and utilized, thereby promoting the growth and development of tomatoes, enhancing the photosynthetic efficiency of plant leaves, and improving the antioxidant capacity of plants. In conclusion, the rational use of water-soluble amino acid fertilizer can significantly facilitate plant seed germination and seedling growth, while foliar spraying of water-soluble amino acid fertilizer significantly promotes the photosynthetic efficiency of plant leaves and the growth of plants. .