The invention relates to a high temperature protective agent for drilling fluid, including 50-70 mass portions of acrylamide, 30-50 portions of di-propylene amide di-methyl miethyl propyl, 20-30 portions of sodium styrene sulfonate, 1-3 portions of thioglycollic acid, 0.5-1.5 portions of ammonium persulfate as initiator with a concentration of 8-15 percent, 0.5-1.5 portion of anhydrous sodium sulfite and pH regulator, acetone as precipitant, and water; the manufacturing technique is: firstly, the acrylamide, the 2-propylene amide-2-methyl miethyl propyl, and the sodium styrene sulfonate are dissolved into 10-20 percent of water solution, then the pH value is regulated to 8-9; nitrogen is filled in to disperse oxygen for 30 minutes and heated to 50-60 DEG C, and then the thioglycollic acid, the ammonium persulfate, the sodium styrene sulfonate are added under constant temperature for 1-8 hours, thus obtaining a gel product which is precipitated and washed with the acetone; reacted substance is removed under the constant temperature of 100-110 DEG C for 1-3 hours; the product is crashed and filtered through a 60 meshed sieve to obtain the high temperature protective agent for drilling fluid. The protective agent has the advantages that the overall thermal resistant property of the sulfonated drilling liquid system can be effectively improved; the cost can be lowered; the application scope can be widened.