To study the fire resistance performance of square timber columns, fire test data were collected, and the charring depth of timber columns was analyzed in detail. An optimization model for predicting the charring rate was provided. Based on the bearing capacity requirements of timber columns, a model for predicting the failure time of timber columns exposed to fire is proposed. The proposed model has high calculation accuracy. In addition, the influence of various design parameters on the failure time of timber columns was discussed. The failure time is significantly affected by factors such as slenderness ratio, cross–sectional size, axial compression ratio, and density. Increasing the slenderness ratio or axial compression ratio will shorten the failure time while increasing the cross–sectional width or wood density will prolong the failure time.