Myostatin is a negative regulator of skeletal muscle mass. The present study cloned the 5' regulatory region of porcine myostatin gene, screened its polymorphisms and analyzed their associations with early growth traits in Yorkshire pigs. The results indicated that a fragment length polymorphism and a polymorphism concerning two nucleotide changes exist in the 5' regulatory region of porcine myostatin gene. At sites 435 and 447, allele A and allele B have the haplotypes of A-G and G-A, respectively. The allelic frequency of B is 0.475 in Yorkshire pigs. No homozygous BB genotype was detected in 9 Laiwu Black pigs. Allele B was found to have positive effect on body weight on day 21 (BW21) (P<0.01), body weight on day 28 (BW28) (P<0.05), body weight on day 70 (BW70) (P<0.05), average daily gain from birth to 21 d (ADG1) (P<0.01), average daily gain from birth to 28 d (ADG2) (P<0.05) and average daily gain from 21 d to 70 d (ADG3) (P<0.01), respectively. The additive effect of allele B on BW21, BW28, BW70, ADG1, ADG2 and ADG3 was 0.596+/-0.205 kg (P=0.0041), 0.498+/-0.200 kg (P=0.0136), 1.409+/-0.551 kg (P=0.0112), 28.39+/-9.74 g P=0.0041), 17.78+/-7.15 g (P=0.0136) and 37.00+/-16.92 g (P=0.0304), respectively, whereas its effect on average daily gain from 28 d to 70 d (ADG4) was not significant (P>0.1), although BB individuals are superior in average daily gain to AA and AB.