The invention discloses a method for welding a tower in vertical assembling mode by utilizing jacks and a crane. The method includes the following steps that firstly, the straightness of all sections of the tower is checked, an end socket of each section of the tower is cut off, and grooves are formed in the end portions of opposite openings of all sections of the tower in a cutting mode; secondly, a lower tower is fixed on a foundation, and the perpendicularity and the elevation of the lower tower are aligned; thirdly, a plurality of first supporting tools are evenly distributed on the peripheral wall of the lower tower, the jacks are distributed on the first supporting tools respectively and adjusted to the same horizontal position, and force measuring instruments are arranged on the jacks; fourthly, a plurality of second supporting tools are evenly distributed on the peripheral wall of the upper tower; fifthly, the upper tower is craned by the crane so that all the second supporting tools can be arranged on the jacks correspondingly, stress on the tops of the jacks is adjusted, the grooves of the end portions of the upper tower and the lower tower are assembled, the perpendicularity of the upper tower and the assembling gap of the upper tower and the lower tower are adjusted, the total carrying capacity of the jacks is N, the carrying capacity of the crane is F, and the weight of the upper tower is Q which is kept to be equal to N+F; sixthly, several welders use the same welding current and meanwhile perform symmetric welding, and therefore welding joints are welded in a multi-layer mode.