The invention discloses a cast-in-place prefabricated composite structure pile suitable for a karst zone and a construction method of the cast-in-place prefabricated composite structure pile. The cast-in-place prefabricated composite structure pile comprises an upper pile section and a lower pile section, the upper pile section is a cast-in-place reinforced concrete grouting pile, the lower pile section is a prefabricated concrete tubular pile, the lower pile section penetrates a karst cave zone in a rock stratum, the upper pile section penetrates a non-karst-cave zone and is supported to theupper end of the lower pile section, and a pile foundation is jointly formed by combining the upper pile section and the lower pile section; in the construction process, an upper-layer non-karst-cavezone pile hole is constructed in a conventional method firstly, then a manual hole digging method or a rotary drilling rig is adopted for constructing a lower-layer karst cave zone pile hole, then theconcrete tubular pile is hoisted into the karst cave zone pile hole, a sealing ring is arranged between the top of the concrete tubular pile and the non-karst-cave zone pile hole, then a reinforcement cage of the reinforced concrete grouting pile is hoisted into the non-karst-cave zone pile hole, and cast-in-place grouting is carried out to obtain the overall pile foundation integrating the concrete tubular pile with the reinforced concrete grouting pile. According to the cast-in-place prefabricated composite structure pile and the construction method, the upper pile section and the lower pile section are combined to form an overall pile body to achieve joint stress, construction is convenient and quick, and the construction cost is low.