The Ruins of St. Paul's is the façade of the Church of Mater Dei and the ruins of St. Paul's College and is one of the monuments of the Historic Centre of Macao which was inscribed in the UNESCO World Heritage List in 2005. The original church was constructed around 1580 by the Jesuits and it was damaged by fire in years of 1595 and 1601. The reconstruction of the church started in 1602 and almost the whole church was re-built. A new front façade of the church was built and finished around 1640. Unfortunately, it experienced a third damage by fire in 1835 and the whole college and church were damaged seriously. Several years after, only the façade of the church and the steps in front of the façade are remained as it is known as the Ruins of St. Paul's nowadays. In this paper, a brief historical background and the current status of the façade is reported. In addition, the structural behaviour of the façade, namely, the dynamic property (the natural frequency) is examined by finite element method. It is found that including the low elastic modulus walls in the finite element model does not have significant effect to the natural frequency of the façade. Also, the finite element results provide useful information for the set up of instruments for monitoring the façade.