Single-shell gas-puff Z-pinch experiments were performed on “Yang” accelerator （peak current 500—850 kA， rise time ～85 ns）. The x-ray power and yield， the time-resolved and time-integrated images of plasma implosions were measured. Based on the corresponding diagnostics， the implosion time was defined and the implosion process was divided into four stages. the initial plasma status and the distribution of radiative intensity were studied. In addition， the implosion trajectories， load mass， radial convergence and magneto- Rayleigh-Taylor （MRT） instability were analyzed.