Expressions of the pulse jitter between lasers in copper vapor laser chains are derived basing on the principle of probability. Results show that: the square of the pulse jittar between two copper vapor lasers equals the square summation of eaoh laser pulse jitter relative to electrical trigger pulse when the copper vapor lasers are in parallel; the laser pulse jitter between mth amplifier and the oscillator increases with m in an oscillator amplifier chain in series, but the jitter is less than 2 times of the jitter of thyratron discharge pulse if each of the thyratron has the same jitter. Experimental results are in agreement with theoretical predictions.