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• A new lamilloy structure equipped with staggered internal minichannels is put forward to achieve an effective cooling. • The lamilloy structure consists of three cooling effects: the impingement cooling, forced convective heat transfer and the film cooling. • The effect on the cooling performance of mass flow ratio and temperature ratio are investigated and compared. The efficiency improvement of the advanced high-power heavy-duty gas turbine will certainly make the design of the combustor develop in the direction of high temperature rise and high heat capacity. Lamilloy cooling is considered the promising cooling structure that can replace the currently commonly used film cooling. This paper proposes a novel long-channel lamilloy cooling structure equipped with internal channels and pin-fins used in combustor flame cylinders, and the cooling and flow characteristics of the proposed structure are studied by combining experiment and simulation. An experimental system is established to explore the cooling characteristic of the proposed structure, and the effect on the cooling characteristic of mass flux ratio (1.07 %∼2.35 %) and temperature ratio (0.5∼0.7) are studied and compared. The cooling effectiveness is found to be increased by 39.62 % when the mass flux ratio increases from 1.07 % to 2.35 % while keeping the temperature ratio at 0.5, and increased by 28.14 % when the temperature ratio increases from 0.5 to 0.7 while keeping the mass flux ratio at 1.07 %. The numerical results show that when T * =0.6, m f * increases from 1.07 % to 2.35 %, the η a increases from 0.469 to 0.628, correspondingly increased by 33.9 %. When m f * =1.93 %, T * increases from 0.5 to 0.7, the η a increases from 0.567 to 0.602, correspondingly increased by 6.27 %, the corresponding increment is weak. The flow field structure shows that strong vortex structures are formed around the pin-fins, and the secondary flow is induced when the coolant flows through the region of the pin-fins, which will enhance the local heat transfer effect. Moreover, the coolant ejecting from the film hole acts as a "baffle", blocking the direct contact between the mainstream and the LLC, playing a similar role to the film cooling. The long-channel lamilloy cooling structure proposed is an effective measure to replace the film cooling, and the research herein provides some reference for designing the combustor flame cylinder cooling structure. [ABSTRACT FROM AUTHOR]