All male Nile tilapia has been one of the most important species for aquaculture in Vietnarn. Application of sex reserval technology by using hormone 17a-Methyl testosterone may have negative effects and risk to environment, foot safety and customer's health. Induction of triploidy (3n) by heat shock or crossing between tetraploidy (4n) and diploidy Nile tilapia is known as an essential solution to control the density and increase economic of tilapia in the culture pond. Study on induced breeding is one of the initial elements in the researches on induction of polyploidy in tilapias. The present study has been carried out to investigate the suitable hormone type and dosage (HCG and a combination of LHRHa and DOM) for inducing the artificial spawning and initial research on heat shock (temperature and duration) to induce polyploidy of Nile tilapia. Three temperature levels (40°C, 41°C and 42°C) and three durations (2 minutes, 3 minutes and 5 minutes) have been tested. The results show that the effected time was from 17-31 hours when female brooder was injected with HCG and the dose of 3,000-3,500 IU/kg, and the spawning rate was 61.11 - 65.56 percent. The average of polyploidy rate of Nile tilapia was highest (58.15 percent 2.75 percent) when the heat shock applied after 65 minutes fertilization for 2 minutes duration at temperature of 42°C.