The symbol length of digital pulse interval modulation (DPIM) is variable, so there are some difficulties to analyze error performances of Turbo coded DPIM. After the analytic model is set up and the error rate is derived, the system error performances of uncoded and Turbo coded DPIM are simulated and analyzed under weak turbulence channel, and the system error performances under Gaussian channel are simulated for comparison. The results show that error performances under weak turbulence channel are inferior to those under Gaussian channel, but for the two channels, introduction of Turbo code can get the code gain of 3～6 dB, which improves the error performance of system effectively and has applied value for military communications.