The invention discloses a natural gas hydrate while-drilling detecting and simulating method based on electromagnetic-thermal-acoustic effect and relates to a detecting while drilling method aiming at deep sea underlying natural gas hydrate, in particular to a natural gas hydrate while-drilling detecting and simulating method based on electromagnetic pulse excitation to inducing phase change of hydrate to generate electromagnetic-thermal-acoustic signals. Two coils are mounted above a drill collar and in a well logging short section; when transient pulse current is fed in, eddy current is excited in a porous medium containing sea water around, and the porous medium is instantly heated to occur phase change and thermal expansion to induce electromagnetic-thermal-acoustic signals. A wave equation of the electromagnetic-thermal-acoustic signals is established with the help of a Maxwell equation and a Clapeyron equation, and a numerical value simulating method for the electromagnetic-thermal-acoustic signals induced by phase change of hydrate.