The invention provides a low-tension foaming agent for improving a non-homogeneous oil reservoir oil recovery factor and an oil displacement method using the same. The low-tension foaming agent for improving a non-homogeneous oil reservoir oil recovery factor comprises, by weight, 40-60% of a main agent, 3-15% of a foam stabilizer, 8-15% of alkyl betaine, 0.1-3% of carboxymethylcellulose and the balance city tap water. The oil displacement method comprises a, adding water into a low-tension foaming agent to obtain an aqueous solution and injecting the aqueous solution as a pre-slug into a low-tension foam displacement water injection well, and b, adding water into the low-tension foaming agent to obtain an aqueous solution, injecting a mixture of the aqueous solution and nitrogen gas, air or natural gas into the low-tension foam displacement water injection well described in the step a, wherein the injection amount is 0.2 to 0.4 times that of the stratum pores, so that an oil displacement foam fluid is formed, and carrying out low-tension foam oil displacement.