In this paper, we provide an analysis of bit error probability (BEP) of two typical relay selection strategies based on threshold-based selection cooperation in detail, at arbitrary signal to noise ratios (SNRs) and number of available relays. We assume that all relays adopt decode-and forward (DF) scheme and all channels follow the Rayleigh fading. One of these two typical strategies has the best the source-to-relay channel (FHSC) and the other has the best the relay-to-destination channel (SHSC). Usually, an approximation will be taken when the selected relay does a wrong decoding. But in this paper, both the situations in which the data, at the relay node, are decoded correctly and not are taken into consideration, precisely. Numerical results demonstrate that when the threshold is low, the source-to-destination link is well and the SNR is relatively high, FHSC will outperform SHSC; otherwise, SHSC will have an advantage over FHSC.