[Objective] This study aims to obtain a novel thermostable mannanase to satisfy industrial application.[Methods] Sequence analysis revealed that the Mtman1 encodes for 409 amino acids (AAs), including a signal peptide and a glycoside hydrolase (GH) 5 catalytic domain. Recombinant MtMAN1 heterologously expressed in Pichia pastoris showed an optimal pH and temperature of 6.0 and 70℃, respectively. The K_m and V_maxvalues of MtMAN1 were 4.28±0.73 mg/mL and 203.9±14.61 μmol/s·mg against locust bean gum, respectively.[Results] The MtMAN1 was stable under 60℃ incubation for 1 h. After treatment at 80℃, 90℃ and 100℃ for 10 min, the enzyme maintained (68.23±7.47)%, (56.01±5.69)% and (14.91±2.92)% residual activities, respectively. Interestingly, its secondary structures and maximum wavelength remained as unchanged, suggesting relatively stable conformational structure. Additionally, the MtMAN1 was considerably resilient to Fe²⁺ (<0.1 mmol/L), Cu²⁺ (<0.1 mmol/L), Ca²⁺ (<0.5 mmol/L), Mg²⁺ (<0.1 mmol/L) or Zn²⁺ (<0.1 mmol/L).[Conclusion] MtMAN1 is a hyperthermostable β-mannanase and could be a candidate for handling industry tanks at high temperatures, such as feed pelleting.