A turbocharger turbine having a double-layer flow passage and a variable cross-section, including a turbine housing, a volute diffuser channel, a power turbine, a volute gas feeding passage, and a partition wall. The volute gas feeding passage is arranged in the turbine housing. The partition wall is arranged in the volute gas feeding passage and divides the volute gas feeding passage into an external volute gas feeding passage and an internal volute gas feeding passage. The external volute gas feeding passage is located outside the internal volute gas feeding passage. The combination of the external and internal volute gas feeding passages forms different flow areas, sufficiently utilizing the waste gas energy of engines in a segmented mode. The variable cross-section turbine has a simple structure, is easy to upgrade at low cost, and can be easily mass-manufactured.