Abstract: Foamed concrete is faced with unstable phenomena such as collapse and defoaming in the process of preparation. Therefore, the stability of foamed concrete must be solved first. In this study, three aspects were explored to solve the problem of foam concrete collapse: adjusting the water-cement ratio, adding foam stabilizer and thickening agent. The results showed that the sample would not collapse at low water ash ratio (< 0.45). When the water cement-ratio exceeded 0.45, the sample began to collapse. The collapse modulus increased with the improvement of water-cement ratio. When the content of CaCl2 was increased from 0% to 0.8%, the collapse values of foamed concrete samples were 0.6 cm, 0.4 cm, 0.35 cm, 0.3 cm and 0 cm respectively. The amount of CaCl2 should be more than 0.8% to ensure that the foam concrete would not collapse. No formwork collapse was founded in foamed concrete samples with silica fume content of 6% and 8%. Foam concrete would not collapse when hydroxypropyl methyl cellulose ether over 0.1%, silica fume content up to 6% and calcium chloride dosage up to 0.8%. This research provides a new method for solving the problem of foam concrete collapse.