Objective To study the effects of different dosages of valproic acid (VPA) in the disease onset, the level of motor dysfunction and survival time to the amyotrophic lateral sclerosis (ALS) model mice. Methods The ALS model mice (hSOD1-G93A gene positive) was screened and genotyped. Then,the model mice were random divided into treated groups( n = 18) and control group( n =6). The treated groups were i.p. injected with different dosage of VPA, but the control group was given isodose of saline. The assessment of the motor dysfunction stared from 12 weeks after birth and continued till death, the onset time and the survival time were recorded and compared. Results High dosage of VPA can prolong the onset time (9. 8 ± 1.4) days( P <0. 05), survival time ( 15.5 ±0. 9) days( P <0. 05), but it was not statistically significant to improve the motor dysfunction for the model mice. Compared with the control group,low and middle dosage of VPA were not statistically significant to prolong the onset time, the survival time for the model mice, and the level of motor dysfunction. Conclusions High dosage of VPA can delay the onset time of the ALS model mice and prolong the survival time, and which has neuroprotective effects against the neuronal degeneration in the hSOD1-G93A-gene-positive model mice.