The invention discloses a main shaft double-position positioning device for a rhombic metal mesh knitting machine, belongs to the technical field of rhombic metal mesh knitting machines, and aims to solve the problems of large impact force, inaccurate positioning and difficulty in repair in the existing positioning way. The main shaft double-position positioning device comprises a main shaft sensor system, a main shaft upper-position positioning electromagnet push rod system, a main shaft upper-position positioning electromagnet push rod system bracket, a main shaft low-position positioning electromagnet push rod system, a main shaft lower-position positioning electromagnet push rod system bracket and a molded structure of two interwoven flat spiral steel wires. By adopting the main shaft double-position positioning device for the rhombic metal mesh knitting machine, the problem that impact and vibration are generated since an electromagnet push rod is directly pressed against the radial surface of a cam without any energy dissipation process, the problems that positioning is inaccurate and adjustment is difficult since an electromagnetic brake has an energy dissipation process as well as a positioning function, and the problems of gasification of oil, pitting corrosion of material surfaces and difficulty in replacing sealing parts in the positioning way of a crank slider mechanism are solved.