The invention provides a symmetrical two-in-one surface casing drilling and completion device and an operation method, belonging to the field of open surface casing drilling and completion. The device comprises a duct arranged in the area of a wellhead slot, wherein a wellbore is arranged in the duct and is vertical; a horizontal two-hole base is arranged on the upper end face of the duct; a first pilot hole and a second pilot hole are formed in the two-hole base; an A well casing column is vertically arranged in the wellbore via the first pilot hole; a B well casing column is vertically arranged in the wellbore via the second pilot hole; the radii of the A well casing column and the B well casing column are the same; the A well casing column and the B well casing column are uniformly distributed relative to the central axis of the wellbore. The device is convenient to operate and has the effects of solving the problem that reservoirs cannot be completely and fully exploited due to lack of platform slots, improving the use efficiency of the wellhead slot and increasing the well spacing density in unit area.