Abstract: Heat shocks were used in this experiment for inducing tetraploids through inhibition o f the first cleavage division in the freshwater prawn Macrobrachium nipponense .Te traploidy prawn embryos had been produced by treating egg s at either 38、39 、40 o r 41 ℃ for 1 ～ 2 minute duration from 210 ～ 230 minutes shortly af ter spawning .At 40 ℃ , shock lasting 1.5 minutes yield 36 .8% tetraploidy embryos .The percentage of mosaics were significantly higher than that of tetraploids at shock of either 39 ℃ for 2 minutes.With shock 41 ℃, the mo rtality of embry os was high due to abono rmal kary okinesis at mitosis.Optional treatment time is needed fo r further investigating in o rder to yield hig h percentages of te traploids .