A key frame selection method in 3D video conversion, comprising: determining (S201, S202, S304) the ( i +1)th key frame based on the i th key frame after the first key frame is determined; calculating (S202, S301, S501) feature matching ratios of video frames after the i th key frame in a 2D video in an ascending order from the first video frame after the i th key frame, comparing each calculated feature matching ratio with T 1, after determining that a feature matching ratio is less than T 1, stopping calculating feature matching ratios of video frames after the i th key frame; wherein the first video frame is determined as the first key frame; wherein, i is a natural number, a feature matching ratio R c j of the j th video frame beginning from the i th key frame is obtained according to the following formula 1; R c j = R j R wherein, j is a natural number, R j is the number of feature points of the j th video frame beginning from the i th key frame, R is the number of feature points of the i th key frame; calculating an overlap area between each video frame with an adjacent video frame; selecting one video frame from candidate key frames each of which has a feature matching ratio within the range of T 1 ∼ T 2 as a key frame; wherein, T 1 and T 2 are thresholds that are configured according to a 3D video quality requirement and wherein T 1 and T 2 are determined according to calculated average value R c of feature matching ratios of video frames after the first frame in the 2D video and calculated average value O ak of change rates of cumulative overlap areas of adjacent video frames in the 2D video, and T 1 < T 2 wherein T 1 is configured according to the following formula 9; T 1 = R c × a × O ak ̅ + b in the formula 9, a and b are preset parameters; and wherein T 2 is configured according to the following formula 10; T 2 = R c × c × O ak ̅ − d in the formula 10, c and d are preset parameters, and wherein a cumulative overlap area of one video frame in the 2D video is obtained according to the following method: the cumulative overlap area O a ( g) of the g th video frame in the 2D video is calculated according to the following formula 8; O a g = ∑ i = 1 g O c i wherein, O c ( g) is the overlap area between the g th video frame and the ( g -1)th video frame in the 2D video, g is a natural number from 2 to the total number of video frames in the 2D video. determining (S201, S202, S304) the ( i +1)th key frame based on the i th key frame after the first key frame is determined; calculating (S202, S301, S501) feature matching ratios of video frames after the i th key frame in a 2D video in an ascending order from the first video frame after the i th key frame, comparing each calculated feature matching ratio with T 1, after determining that a feature matching ratio is less than T 1, stopping calculating feature matching ratios of video frames after the i th key frame; wherein the first video frame is determined as the first key frame; wherein, i is a natural number, a feature matching ratio R c j of the j th video frame beginning from the i th key frame is obtained according to the following formula 1; R c j = R j R wherein, j is a natural number, R j is the number of feature points of the j th video frame beginning from the i th key frame, R is the number of feature points of the i th key frame; calculating an overlap area between each video frame with an adjacent video frame; selecting one video frame from candidate key frames each of which has a feature matching ratio within the range of T 1 ∼ T 2 as a key frame; wherein, T 1 and T 2 are thresholds that are configured according to a 3D video quality requirement and wherein T 1 and T 2 are determined according to calculated average value R c of feature matching ratios of video frames after the first frame in the 2D video and calculated average value O ak of change rates of cumulative overlap areas of adjacent video frames in the 2D video, and T 1 < T 2 wherein T 1 is configured according to the following formula 9; T 1 = R c × a × O ak ̅ + b in the formula 9, a and b are preset parameters; and wherein T 2 is configured according to the following formula 10; T 2 = R c × c × O ak ̅ − d in the formula 10, c and d are preset parameters, and wherein a cumulative overlap area of one video frame in the 2D video is obtained according to the following method: the cumulative overlap area O a ( g) of the g th video frame in the 2D video is calculated according to the following formula 8; O a g = ∑ i = 1 g O c i wherein, O c ( g) is the overlap area between the g th video frame and the ( g -1)th video frame in the 2D video, g is a natural number from 2 to the total number of video frames in the 2D video. the cumulative overlap area O a ( g) of the g th video frame in the 2D video is calculated according to the following formula 8; O a g = ∑ i = 1 g O c i wherein, O c ( g) is the overlap area between the g th video frame and the ( g -1)th video frame in the 2D video, g is a natural number from 2 to the total number of video frames in the 2D video.