Disclosed are a flexible polymer, particles made from same, and a process for preparing the particles. This flexible polymer is obtained from copolymerizing monomer (A) and monomer (B), wherein monomer (A) is one or more water-insoluble unsaturated diene monomers; monomer (B) is at least one compound with the general formula of wherein R is C1-C12alkyl, C1-C12 alkyl aryl, C1-C12 alkyl ether or C1-C12alkyl ester. Monomer (A) is in an amount of 60-90% by weight of the total combined weight of monomer (A) and monomer (B). Monomer (B) is in an amount of 10-40% by weight of the total combined weight of monomer (A) and monomer (B). The flexible polymer particles show excellent flexibility, deformability, elasticity as well as stability. They can be used in oilfields in nearby wellbore profile control and in-depth profile control or as in-depth flooding fluid diverting agents. They can also be applied in water shutoff in high temperature and high salinity production wells; preventing chemical channeling in polymer and ASP (alkali-surfactant-polymer) flooding; temporarily plugging in acidization; huff and puff; and preventing in-depth channeling in steam flooding, loss of circulation control and filtration control, and the like.