We propose a theoretical model (cavityless pulsed solid-state-laser theory) to analyze the pulse characteristics of cavity-less solid-state lasers.A high gain Nd:YVO4 end-pumped cavityless laser system is adopted to verify the theoretical model.It shows that the performance of output energy and pulse width achieved in cavityless configuration is better than that in resonator configuration when the small-signal gain reaches the saturated level.The simulation results calculated by our theoretical model agree very well with the experimental results.This agreement proves the validity of our theoretical model,which has great importance for theoretical analyses of high gain pulsed laser.