Background <p>The rapid development of intensive layer breeding has intensified odor pollution that must be paid attention to for the green transformation of the industry. This study used Jingfen No.6 laying hens as the model to systematically evaluate the regulatory effect of compound microalgal powder (<i>Chlorella vulgaris</i>:<i>Spirulina platensis</i>:<i>Haematococcus pluvialis</i> = 3:1:1, 1:3:1, 1:1:3) on ammonia (NH₃) emissions from laying hen manure.</p> Results <p>Through analysis of the static NH₃ production in manure, it was found that the NH₃ emissions within 24&#xa0;h in the experimental group with 0.50% compound microalgal powder added were reduced to 6.27–16.84&#xa0;mg (vs. control: 28.29&#xa0;mg), achieving a 40.47%–77.84% reduction. GC/MS and 16S rRNA sequencing analyses indicated that the compound microalgal powder intervened in the remodeling of the microbial community and nitrogen metabolism network in manure, driving the transformation from inorganic nitrogen to organic nitrogen, mitigated the proliferation of NH₃-producing bacteria (such as <i>Escherichia coli</i>, <i>Klebsiella pneumoniae</i>, <i>Kurthia</i>, and <i>Proteus</i>), and increased the abundance of acid-producing bacteria (such as Leuconostocaceae&#xa0;and Lactobacillaceae). The <i>Spirulina platensis</i> powder group had the best emission reduction effect (reduced by 77.84%), and its mechanism was closely related to the mitigation of Gram-negative bacteria activity by phycocyanin and increased synthesis of aromatic compounds, such as 2,3,5-trimethyl-6-ethylpyrazine.</p> Conclusions <p>This study revealed the mechanism by which the compound microalgal powder reduces NH₃ emissions by regulating the proliferation of acid-producing bacteria, reshaping the nitrogen metabolism network, and mitigating the activity of NH₃-producing bacteria, while providing theoretical and data support for the development of environmentally friendly feed.</p> Graphical Abstract <p></p>