A new analytical model for VOCs emission was presented. Compared with other models, it takes into account the situation in which the initial concentrations of VOCs in the room and the inlet concentration are not zero. The results are in good agreement with the experiment results and the discrete solution of equations. Moreover, the form of the solution is completely analytical, so it can be calculated without iteration. Therefore, this model can be used more widely. Finally, this model can be used in three ways: first, we can calculate the concentration of VOCs in a room; second, we can calculate the amount of VOCs emitted from building materials; and third, we can also calculate the ventilation time or ventilation rate with the given building materials and the concentration of VOCs in a room. This provides the basis for the design of airconditioning systems.