An electrical connector includes an insulative housing having a longitudinal slot and at least one row of contacts retained in the housing. Each of the contacts defines a retention portion, a resilient contacting arm extending from the retention portion with a contacting portion protruding into the longitudinal slot, and a soldering tail extending out of the housing. The contacts include at least two differential pairs adjacent to each other and at least one grounding contact sandwiched therebetween in the longitudinal direction. The contacting portions of each differential pairs are closer to the mating face than the contacting portion of the grounding contact in the mating direction, which can improve resonance of the electrical connector during transferring high-speed signals.