Phosphorus compounds have been intensively investigated as potential negative electrode materials of alkali-metal (AM) ion batteries. However, the practical application is greatly hindered by the low conductivity due to the semiconducting nature of phosphorus and rapid structural degradation during cycling. Based on first-principles calculations, we proposed a new two-dimensional phosphorus carbide compound β 0-PC monolayer (PCM) as a promising anode material for AM (AM = Li, Na, and K) ion batteries. The PCM exhibits excellent electric conductivity and high charge/discharge rate due to the low energy barriers for the diffusion of AM atoms, 66 (Li), 39 (Na) and 36 meV (K). The storage capacities of AM ions are Li, Na and K atoms on PCM can be as high as 1247.1 mA h g−1 (Li) 623.5 mA h g−1(Na), and 623.5 mA h g−1(K), respectively. More importantly, the PCM possesses ultrahigh stiffness (C x = 186.08 J/m2 (zigzag), C y = 123.16 J/m2 (armchair)) which can effectively avoid structure degradation during discharging/charging cycles. These interesting properties open avenue to overcome the drawbacks of phosphorus compounds in the AM ion batteries.