In Jeon et al. (2010), a cooperative PNG (Proportional Navigation Guidance) law was proposed to achieve the salvo attack using multiple missiles. When the leading angle is near zero, singularity would occur, and the cooperation may fail. In this paper, a modified cooperative guidance law is presented to avoid such singularity existing in the guidance law in Jeon et al. (2010). The time-to-go control efficiency under small leading angle is also improved in this paper. The convergence of times-to-go to the same value using the proposed guidance law is guaranteed by the Lyapunov stability analysis. Simulation results show the effectiveness of the modified guidance law and the improved performance.