The increasing number of space debris has drawn public attentions, as the safety of spacecraft is severely threatened. Luckily, high-repetition-rate laser ranging technology provides an effective way for space debris measurements. The high repetition rate of laser pulses brings along a large sample quantity, while there is little research about the demanded sample quantity for the needed ranging precision. In this study, the effect of sample quantity on ranging precision is researched based on the high-repetition sampling, and the minimum sample quantity is obtained. Firstly, the orbit elements of space debris is applied as the priori information for preprocessing. Then the effective samples are obtained by polynomial fitting and iteration. By gradually decreasing the sample quantity, a precision-sample quantity curve is drawn, where the minimum sample quantity can be estimated form the threshold in the curve. Based on the minimum sample quantity, the transmitted repetition rate of the laser ranging system can be adjusted. Experimental results for some space debris show that the effective sample quantity can be decreased by about 30%-60% based on the current system parameters.