The invention discloses a step-by-step excavation construction method for an intersection of an inclined shaft and a main tunnel. The standard section of the main tunnel is gradually formed as shown in figures 2 and 3 through step-by-step excavation after inclined shaft construction to a main tunnel junction. According to the step-by-step excavation construction method, the construction time can be shortened, the construction cost can be reduced, the construction security is improved and the economic benefit is significant. The inclined shaft is constructed to a second section of the main tunnel junction, an extension axis and an excavation section enter the main tunnel, and an arch crown is lifted and an outline is excavated to the arch crown of the main tunnel along the main tunnel in an uphill manner at the same time; the outline is excavated to a springing line (a third section) along the main tunnel in a downhill manner; the outline (the segment from the second section to the third section) is excavated by employing the arch crown of the inclined shaft as the main tunnel and the first section is prolonged, the standard section of the main tunnel is formed through excavating towards two ends of the main tunnel separately; and then an area between the third section and the fourth section of the main tunnel is excavated to form the standard section of the main tunnel, so that the whole standard section of the main tunnel is formed.