In this study, a monitoring system of cognitive state in usual behavior without restraint using wireless EEG, ECG and NIRS on developmental disorder children such as mental retardation was developed. By using this system we would like to investigate the education training effect on cognitive state in a mental retardation child in four years. The aim of special education is to make adaptations, accommodations and modification that allow a child with a mental retardation to succeed in classroom. This education training separated into two systems, resting state and studying state. After the measurement, we calculated the EEG power spectrum of alpha, theta bands and the low frequency power (LF), high frequency power (HF), and LH/HF value from the RR interval in ECG. At the same time we calculated the changes in concentration of oxyhemoglobin ([oxy-Hb]). The result in studying state showed theta power is lower than beta power in study state in the other hand beta power is lower than theta power in resting state From LF/HF activity we could know that sympathetic activity is increasing and from the result that has obtained from ECG, the parasympathetic activity is decreasing the time. NIRS showed the increasing in study states and decreasing in resting states at Fp2 area from oxyhemoglobin analysis.