The effects of the amount of foaming agent on surface morphology and pores diameter, strength, density, thermal conductivity and utilization efficiency of foam concrete are investigated. Results show that foam concrete can get the best performance when the amount of foaming agent added in 5%6% of the total foam concrete, and the utilization efficiency of foaming agent is the best. Microscopic structure of the foam concrete and theoretical calculation are adopted to explain the result. Foaming agent utilization efficiency and the best addition amount of foaming agent have a certain theoretical guiding significance for foam concrete production.