Abstract: In order to address the problems of water resistance, poor weather resistance and potential formaldehyde release of urea-formaldehyde resins, lignin-based adhesives(LPUs) with ultra-low formaldehyde emission meeting the requirements of E_NF grade Ⅰ plywood were prepared by co-condensation with phenol(P), urea(U) and industrial alkali lignin(L). The effects of L, P and U mass ratio on the gel time, free formaldehyde content, storage stability, curing reaction activity and physicochemical properties of LPUs were investigated. The results showed that the maximum ratio of m_L/(m_P+m_U) was up to 1∶1. With the decreasing mass ratio of P and U, the gel time of LPUs resin was gradually shortened by 40%, the free formaldehyde content increased from 0.05% to 0.18%, and the storage period was reduced from 127 d to 14 d, showing the physical and chemical properties of urea-formaldehyde resins. The enthalpy change behavior of the curing process monitored by DSC showed that the reaction activation energy of LPUs resin only reached 2%-7.8% of that of commercial phenolic and urea-formaldehyde resins. The boiling water resistance and formaldehyde emission of LPU1-LPU4 resin plywood prepared with m_L/(m_P+m_U)=1 and with the amount of phenol not less than that of urea, met the requirements of E_NF grade Ⅰ plywood. The glue spread of LPU2 resin could be reduced to 66.7% compared to that of the industrial production process. At this time, the boiling water resistance and formaldehyde emission of plywood could still be ensured to meet the requirements of E_NF grade Ⅰ, which could effectively reduce the production cost of plywood.