Abstract: Biomass pyrolysis can produce high-value chemicals, hydrogen-rich gases, and premium biochar. Cellulose is the most abundant and structural component of biomass. Its pyrolysis behavior can directly govern the yield and quality of biomass pyrolysis products. Natural biomass is universally rich in AAEMs, which are key endogenous catalytic factor that fundamentally changes the pyrolysis reaction pathway, compared with pure cellulose pyrolysis. Most existing studies have focused only on the catalytic effect of single metal cations, without matching acid radical anions. Synergistic catalytic mechanisms then limit precise control of pyrolysis products. This study aims to elucidate the effects of alkali and alkaline earth metals (AAEMs) and their acid radical anions on the three-phase (gas, liquid, and solid) product distribution during cellulose pyrolysis. Cellulose was taken as the model compound. Different types (K+, Na⁺, Ca²⁺, Mg²⁺) and concentrations (0.25, 1.0, and 2.5 mmol/g cellulose) of AAEMs were introduced via impregnation. A systematic investigation was undertaken to explore the effects of various acid radical anions (SO₄^2-, CO₃^2-, Cl^-, HCO₃^-, CH₃COO^-, PO₄^3-) on the catalytic behavior of K⁺. Pyrolysis experiments were conducted in a fixed-bed reactor at 550 ℃ under an N₂ atmosphere. Gas composition and bio-oil components were determined by Gas Chromatography (GC) and Mass Spectrometer (MS) (peak area normalization). Biochar was analyzed by ultimate/proximate analysis and calorific value measurement. The results demonstrate that the type of AAEM determined the product distribution. Alkaline earth metals (Ca²⁺, and Mg²⁺) exhibited stronger catalytic activity than alkali metals (K⁺, Na⁺), thus promoting biochar formation to suppress the bio-oil yield. In gaseous products, alkali metals favored CO generation (up to 68.02 % under K⁺ catalysis), whereas alkaline earth metals preferentially enhanced CO₂ production. In liquid products, alkali metals promoted the accumulation of sugars (up to 31.79% with KCl), while alkaline earth metals strongly catalyzed the enrichment of furans (up to 76.1% with CaCl₂). Lewis's acidity and cations' coordination were attributed to glycosidic bond cleavage, dehydration, and ring-opening reactions. Furthermore, the acid radical anions finely modulated the catalytic selectivity of K⁺. The biochar yield followed the descending order of: K3PO4, K₂CO₃, K₂SO₄, KHCO₃, KCl ≈ CH₃COOK. Notably, CH₃COOK and K₂CO₃ significantly promoted H₂ generation (up to 26.34%), while PO₄^3- uniquely enhanced CO selectivity (up to 64.94%). In terms of bio-oil composition, K₂CO₃ and KHCO₃ mainly promoted the formation of ketones, alcohols, esters, and hydrocarbons (total 65%-85%), with undetectable furans and acetals. In contrast, the potassium salts (K₂SO₄, K₃PO₄, CH₃COOK, and KCl) led to a more complex distribution of products: KCl and K₂SO₄ favored sugar formation, whereas K₃PO₄ and CH₃COOK promoted carboxylic acids, ketones, and furans. These variations were attributed to the different basicity, coordination and thermal stability among the anions, which influenced dehydration, decarboxylation, and secondary cracking pathways. The coupling effect of cations and anions can be used to clarify the respective regulation of AAEM types, concentrations and acid radical species on three-phase products. There were synergistic catalytic roles of AAEMs and their associated anions in cellulose pyrolysis. Metal cations and acid radical anions were rationally matched to directionally regulate product distribution, gas composition, and bio-oil chemical structure. The findings can provide a solid theoretical basis and technical support for the high-value production and clean utilization of biomass energy resources.iochar from biomass pyrolysis.