A slide rail assembly for an electronic cabinet, comprising: a first rail (18, 208) comprising a first wall (28a, 210), a second wall and a longitudinal wall connected between the first wall (28a, 210) and the second wall, a passage being defined by the first wall (28a, 210), the second wall and the longitudinal wall, the passage having a first height; and a second rail (20, 200) movable relative to the first rail (18, 208), the second rail (20, 200) comprising a main body part and an extension part (34, 202), the main body part having a second height, an end of the extension part (34, 202) having a third height; wherein the first height of the passage of the first rail (18, 208) is greater than the second height of the main body part of the second rail (20, 200), and the second height of the main body part of the second rail (20, 200) is greater than the third height of the end of the extension part (34, 202); wherein the extension part (34, 202) is configured to be operatively placed into the passage of the first rail (18, 208) to directly contact the first wall (28a, 210) of the first rail (18, 208), in order to guide the main body part of the second rail (20, 200) to enter the passage of the first rail (18, 208). characterized by: wherein the main body part of the second rail (20, 200) comprises a first wall (36a, 204) straightly elongated along a longitudinal direction of the second rail (20, 200), a second wall (36b, 206) straightly elongated along the longitudinal direction of the second rail (20, 200), and a longitudinal wall connected between the first wall (36a, 204) and the second wall (36b, 206), the first wall (36a, 204) of the second rail (20, 200) is straightly extended from the main body part to the end of the extension part (34, 202) along the longitudinal direction of the second rail (20, 200), the second wall (36b, 206) of the second rail (20, 200) is not extended to the extension part (34, 202); wherein the extension part comprises a guiding surface located between the first wall and the second wall of the second rail, and the guiding surface is an inclined surface or a curved surface. a first rail (18, 208) comprising a first wall (28a, 210), a second wall and a longitudinal wall connected between the first wall (28a, 210) and the second wall, a passage being defined by the first wall (28a, 210), the second wall and the longitudinal wall, the passage having a first height; and a second rail (20, 200) movable relative to the first rail (18, 208), the second rail (20, 200) comprising a main body part and an extension part (34, 202), the main body part having a second height, an end of the extension part (34, 202) having a third height; wherein the first height of the passage of the first rail (18, 208) is greater than the second height of the main body part of the second rail (20, 200), and the second height of the main body part of the second rail (20, 200) is greater than the third height of the end of the extension part (34, 202); wherein the extension part (34, 202) is configured to be operatively placed into the passage of the first rail (18, 208) to directly contact the first wall (28a, 210) of the first rail (18, 208), in order to guide the main body part of the second rail (20, 200) to enter the passage of the first rail (18, 208). characterized by: wherein the main body part of the second rail (20, 200) comprises a first wall (36a, 204) straightly elongated along a longitudinal direction of the second rail (20, 200), a second wall (36b, 206) straightly elongated along the longitudinal direction of the second rail (20, 200), and a longitudinal wall connected between the first wall (36a, 204) and the second wall (36b, 206), the first wall (36a, 204) of the second rail (20, 200) is straightly extended from the main body part to the end of the extension part (34, 202) along the longitudinal direction of the second rail (20, 200), the second wall (36b, 206) of the second rail (20, 200) is not extended to the extension part (34, 202); wherein the extension part comprises a guiding surface located between the first wall and the second wall of the second rail, and the guiding surface is an inclined surface or a curved surface. wherein the main body part of the second rail (20, 200) comprises a first wall (36a, 204) straightly elongated along a longitudinal direction of the second rail (20, 200), a second wall (36b, 206) straightly elongated along the longitudinal direction of the second rail (20, 200), and a longitudinal wall connected between the first wall (36a, 204) and the second wall (36b, 206), the first wall (36a, 204) of the second rail (20, 200) is straightly extended from the main body part to the end of the extension part (34, 202) along the longitudinal direction of the second rail (20, 200), the second wall (36b, 206) of the second rail (20, 200) is not extended to the extension part (34, 202); wherein the extension part comprises a guiding surface located between the first wall and the second wall of the second rail, and the guiding surface is an inclined surface or a curved surface.